Remove unused methods on ShippingMethod
Remove unused methods on ShippingMethod

compute_amount is private and unused in the class

the two "query" calls are both class methods and therefore usable
externally, even though they're marked "private" but aren't used
anywhere in the project

Fixes #5909

NerdsvilleCEO/spree,vcavallo/spree,AgilTec/spree,raow/spree,raow/spree,maybii/spree,JDutil/spree,lyzxsc/spree,Engeltj/spree,TrialGuides/spree,siddharth28/spree,ayb/spree,yushine/spree,tomash/spree,TrialGuides/spree,SadTreeFriends/spree,vinsol/spree,jimblesm/spree,sunny2601/spree,reidblomquist/spree,ramkumar-kr/spree,shekibobo/spree,DynamoMTL/spree,assembledbrands/spree,tesserakt/clean_spree,rakibulislam/spree,hifly/spree,carlesjove/spree,archSeer/spree,edgward/spree,pervino/spree,welitonfreitas/spree,agient/agientstorefront,groundctrl/spree,useiichi/spree,cutefrank/spree,builtbybuffalo/spree,moneyspyder/spree,grzlus/spree,caiqinghua/spree,dafontaine/spree,tesserakt/clean_spree,thogg4/spree,carlesjove/spree,carlesjove/spree,Boomkat/spree,lyzxsc/spree,azclick/spree,Lostmyname/spree,sideci-sample/sideci-sample-spree,omarsar/spree,locomotivapro/spree,joanblake/spree,nooysters/spree,progsri/spree,sfcgeorge/spree,jaspreet21anand/spree,zamiang/spree,progsri/spree,sunny2601/spree,gautamsawhney/spree,fahidnasir/spree,rajeevriitm/spree,vinayvinsol/spree,miyazawatomoka/spree,DarkoP/spree,yiqing95/spree,welitonfreitas/spree,tesserakt/clean_spree,karlitxo/spree,softr8/spree,ayb/spree,CiscoCloud/spree,orenf/spree,piousbox/spree,jasonfb/spree,vinsol/spree,vinsol/spree,jimblesm/spree,kewaunited/spree,calvinl/spree,azclick/spree,archSeer/spree,azranel/spree,volpejoaquin/spree,odk211/spree,shaywood2/spree,njerrywerry/spree,ahmetabdi/spree,odk211/spree,rbngzlv/spree,welitonfreitas/spree,vulk/spree,gregoryrikson/spree-sample,zaeznet/spree,derekluo/spree,Machpowersystems/spree_mach,calvinl/spree,Ropeney/spree,priyank-gupta/spree,Machpowersystems/spree_mach,alvinjean/spree,tomash/spree,hoanghiep90/spree,softr8/spree,adaddeo/spree,cutefrank/spree,mindvolt/spree,gregoryrikson/spree-sample,alvinjean/spree,raow/spree,maybii/spree,FadliKun/spree,robodisco/spree,DynamoMTL/spree,Kagetsuki/spree,JuandGirald/spree,FadliKun/spree,reidblomquist/spree,Boomkat/spree,shaywood2/spree,reinaris/spree,jaspreet21anand/spree,camelmasa/spree,tesserakt/clean_spree,grzlus/spree,karlitxo/spree,priyank-gupta/spree,cutefrank/spree,pulkit21/spree,radarseesradar/spree,piousbox/spree,assembledbrands/spree,Engeltj/spree,carlesjove/spree,Boomkat/spree,alejandromangione/spree,Lostmyname/spree,robodisco/spree,vcavallo/spree,APohio/spree,derekluo/spree,shekibobo/spree,abhishekjain16/spree,adaddeo/spree,TimurTarasenko/spree,sideci-sample/sideci-sample-spree,thogg4/spree,nooysters/spree,tancnle/spree,Lostmyname/spree,NerdsvilleCEO/spree,wolfieorama/spree,abhishekjain16/spree,kewaunited/spree,edgward/spree,jspizziri/spree,tomash/spree,kewaunited/spree,camelmasa/spree,groundctrl/spree,jparr/spree,siddharth28/spree,alejandromangione/spree,reinaris/spree,delphsoft/spree-store-ballchair,CJMrozek/spree,beni55/spree,jspizziri/spree,lsirivong/spree,hoanghiep90/spree,mindvolt/spree,vcavallo/spree,shekibobo/spree,SadTreeFriends/spree,jaspreet21anand/spree,agient/agientstorefront,grzlus/spree,fahidnasir/spree,zamiang/spree,berkes/spree,ahmetabdi/spree,gautamsawhney/spree,fahidnasir/spree,azranel/spree,imella/spree,KMikhaylovCTG/spree,yushine/spree,TrialGuides/spree,vinayvinsol/spree,imella/spree,jasonfb/spree,ahmetabdi/spree,zaeznet/spree,APohio/spree,keatonrow/spree,beni55/spree,CJMrozek/spree,brchristian/spree,volpejoaquin/spree,beni55/spree,keatonrow/spree,pervino/spree,fahidnasir/spree,delphsoft/spree-store-ballchair,archSeer/spree,omarsar/spree,kewaunited/spree,vcavallo/spree,priyank-gupta/spree,beni55/spree,miyazawatomoka/spree,firman/spree,gautamsawhney/spree,AgilTec/spree,odk211/spree,patdec/spree,JDutil/spree,madetech/spree,calvinl/spree,mindvolt/spree,joanblake/spree,vmatekole/spree,siddharth28/spree,zamiang/spree,groundctrl/spree,njerrywerry/spree,abhishekjain16/spree,pervino/spree,Machpowersystems/spree_mach,quentinuys/spree,progsri/spree,trigrass2/spree,ayb/spree,alvinjean/spree,DarkoP/spree,calvinl/spree,derekluo/spree,Hawaiideveloper/shoppingcart,mindvolt/spree,keatonrow/spree,sliaquat/spree,nooysters/spree,thogg4/spree,yiqing95/spree,zaeznet/spree,karlitxo/spree,maybii/spree,vmatekole/spree,gregoryrikson/spree-sample,lyzxsc/spree,jparr/spree,assembledbrands/spree,JuandGirald/spree,locomotivapro/spree,azclick/spree,agient/agientstorefront,hoanghiep90/spree,jparr/spree,camelmasa/spree,radarseesradar/spree,moneyspyder/spree,dandanwei/spree,builtbybuffalo/spree,derekluo/spree,trigrass2/spree,dandanwei/spree,progsri/spree,lsirivong/spree,JuandGirald/spree,Hawaiideveloper/shoppingcart,Ropeney/spree,camelmasa/spree,ramkumar-kr/spree,NerdsvilleCEO/spree,pervino/spree,softr8/spree,caiqinghua/spree,delphsoft/spree-store-ballchair,rakibulislam/spree,agient/agientstorefront,rbngzlv/spree,KMikhaylovCTG/spree,jimblesm/spree,locomotivapro/spree,brchristian/spree,sliaquat/spree,pulkit21/spree,jspizziri/spree,rakibulislam/spree,volpejoaquin/spree,miyazawatomoka/spree,raow/spree,ahmetabdi/spree,NerdsvilleCEO/spree,Hawaiideveloper/shoppingcart,locomotivapro/spree,vulk/spree,njerrywerry/spree,shekibobo/spree,Ropeney/spree,alejandromangione/spree,yiqing95/spree,berkes/spree,jeffboulet/spree,jaspreet21anand/spree,jeffboulet/spree,karlitxo/spree,patdec/spree,jimblesm/spree,hifly/spree,robodisco/spree,jparr/spree,gautamsawhney/spree,quentinuys/spree,JDutil/spree,madetech/spree,adaddeo/spree,moneyspyder/spree,tancnle/spree,useiichi/spree,CiscoCloud/spree,JuandGirald/spree,patdec/spree,rakibulislam/spree,ramkumar-kr/spree,miyazawatomoka/spree,delphsoft/spree-store-ballchair,wolfieorama/spree,KMikhaylovCTG/spree,reinaris/spree,Boomkat/spree,pulkit21/spree,trigrass2/spree,mleglise/spree,madetech/spree,trigrass2/spree,sliaquat/spree,vulk/spree,hifly/spree,CJMrozek/spree,grzlus/spree,Kagetsuki/spree,sfcgeorge/spree,lsirivong/spree,patdec/spree,Lostmyname/spree,jasonfb/spree,azclick/spree,APohio/spree,TimurTarasenko/spree,sfcgeorge/spree,builtbybuffalo/spree,Hawaiideveloper/shoppingcart,rbngzlv/spree,caiqinghua/spree,volpejoaquin/spree,vinayvinsol/spree,dafontaine/spree,gregoryrikson/spree-sample,ramkumar-kr/spree,vmatekole/spree,keatonrow/spree,wolfieorama/spree,lyzxsc/spree,maybii/spree,pulkit21/spree,CiscoCloud/spree,wolfieorama/spree,firman/spree,mleglise/spree,APohio/spree,cutefrank/spree,TimurTarasenko/spree,dafontaine/spree,Kagetsuki/spree,alejandromangione/spree,CJMrozek/spree,ayb/spree,Ropeney/spree,moneyspyder/spree,orenf/spree,yiqing95/spree,quentinuys/spree,radarseesradar/spree,sliaquat/spree,azranel/spree,orenf/spree,berkes/spree,useiichi/spree,vulk/spree,edgward/spree,jasonfb/spree,builtbybuffalo/spree,jspizziri/spree,KMikhaylovCTG/spree,DarkoP/spree,jeffboulet/spree,joanblake/spree,vinayvinsol/spree,azranel/spree,alvinjean/spree,mleglise/spree,groundctrl/spree,sunny2601/spree,shaywood2/spree,siddharth28/spree,tomash/spree,rajeevriitm/spree,vinsol/spree,SadTreeFriends/spree,joanblake/spree,sfcgeorge/spree,radarseesradar/spree,robodisco/spree,berkes/spree,sideci-sample/sideci-sample-spree,tancnle/spree,jeffboulet/spree,madetech/spree,Engeltj/spree,reidblomquist/spree,softr8/spree,AgilTec/spree,rajeevriitm/spree,abhishekjain16/spree,DarkoP/spree,AgilTec/spree,rbngzlv/spree,SadTreeFriends/spree,TimurTarasenko/spree,Kagetsuki/spree,odk211/spree,vmatekole/spree,zamiang/spree,orenf/spree,imella/spree,piousbox/spree,archSeer/spree,DynamoMTL/spree,Engeltj/spree,thogg4/spree,adaddeo/spree,hoanghiep90/spree,lsirivong/spree,sunny2601/spree,zaeznet/spree,reinaris/spree,dandanwei/spree,caiqinghua/spree,piousbox/spree,TrialGuides/spree,rajeevriitm/spree,yushine/spree,shaywood2/spree,njerrywerry/spree,FadliKun/spree,welitonfreitas/spree,reidblomquist/spree,omarsar/spree,dandanwei/spree,dafontaine/spree,nooysters/spree,firman/spree,quentinuys/spree,DynamoMTL/spree,omarsar/spree,firman/spree,useiichi/spree,tancnle/spree,brchristian/spree,brchristian/spree,FadliKun/spree,mleglise/spree,JDutil/spree,yushine/spree,edgward/spree,priyank-gupta/spree,CiscoCloud/spree,hifly/spree