Travis CI: Use Ruby 2.2.
Travis CI: Use Ruby 2.2.

Fixes #18225.

[skip sauce]

jipexu/bootstrap,gijsbotje/bootstrap,inway/bootstrap,peterblazejewicz/bootstrap,janseliger/bootstrap,slavanga/bootstrap,blockstack/blockstack-bootstrap,gijsbotje/bootstrap,JumpLinkNetwork/bootstrap-backward,bardiharborow/bootstrap,inway/bootstrap,hebbet/bootstrap,yuyokk/bootstrap,tagliala/bootstrap,GerHobbelt/bootstrap,wesamco/bootstrap-rtl,urbit/bootstrap,n054/bootstrap,xt0rted/bootstrap,vsn4ik/bootstrap,Delagen/bootstrap,andresgalante/bootstrap,GerHobbelt/bootstrap,fschumann1211/bootstrap,frostbitten/bootstrap,NCARB/bootstrap,SweetProcess/bootstrap,stanwmusic/bootstrap,tomlutzenberger/bootstrap,tomlutzenberger/bootstrap,vitaligent/4,sealocal/bootstrap,hebbet/bootstrap,Hemphill/bootstrap-docs,SweetProcess/bootstrap,Hightrack/bootstrap,joblocal/bootstrap,copperdesign/bootstrap,stanwmusic/bootstrap,Scoutski/bootstrap,SweetProcess/bootstrap,hebbet/bootstrap,tagliala/bootstrap,johnajacob/bootstrap,seanwu99/bootstrap,nice-fungal/bootstrap,coliff/bootstrap,Lyricalz/bootstrap,onenameio/rhythm-bootstrap,n054/bootstrap,davethegr8/bootstrap,tagliala/bootstrap,tibo66/bootstrap,9-chirno/chirno,IdanCo/bootstrap,yuyokk/bootstrap,nice-fungal/bootstrap,blockstack/blockstack-bootstrap,bootstrapbrasil/bootstrap,kvlsrg/bootstrap,JumpLinkNetwork/bootstrap-backward,david-schopf/bootstrap,seanwu99/bootstrap,GerHobbelt/bootstrap,edanbarak/bootstrap,jipexu/bootstrap,frostbitten/bootstrap,joblocal/bootstrap,copperdesign/bootstrap,gijsbotje/bootstrap,vitaligent/4,tibo66/bootstrap,abvalentine/bootstrap,seanwu99/bootstrap,kvlsrg/bootstrap,mpharrigan/bootstrap,davethegr8/bootstrap,david-schopf/bootstrap,lipis/bootstrap,slavanga/bootstrap,lemuelbarango/bootstrap,Lyricalz/bootstrap,IdanCo/bootstrap,lemuelbarango/bootstrap,lemuelbarango/bootstrap,slavanga/bootstrap,NCARB/bootstrap,abvalentine/bootstrap,JumpLinkNetwork/bootstrap-backward,afuno/bootstrap,johnajacob/bootstrap,bardiharborow/bootstrap,hebbet/bootstrap,fschumann1211/bootstrap,onenameio/rhythm-bootstrap,seanwu99/bootstrap,supergibbs/bootstrap,kvlsrg/bootstrap,hellonewman81/bs4,9-chirno/chirno,copperdesign/bootstrap,janseliger/bootstrap,bootstrapbrasil/bootstrap,JumpLinkNetwork/bootstrap-backward,TheFridayInstitute/bootstrap,stanwmusic/bootstrap,joblocal/bootstrap,urbit/bootstrap,NCARB/bootstrap,Delagen/bootstrap,Scoutski/bootstrap,tjkohli/bootstrap,Hemphill/bootstrap-docs,supergibbs/bootstrap,nice-fungal/bootstrap,realcrowd/bootstrap,johnajacob/bootstrap,edanbarak/bootstrap,Delagen/bootstrap,xt0rted/bootstrap,davethegr8/bootstrap,vsn4ik/bootstrap,fschumann1211/bootstrap,TheFridayInstitute/bootstrap,edanbarak/bootstrap,creativewebjp/bootstrap,johnajacob/bootstrap,vsn4ik/bootstrap,peterblazejewicz/bootstrap,realcrowd/bootstrap,hellonewman81/bs4,slavanga/bootstrap,afuno/bootstrap,twbs/bootstrap,janseliger/bootstrap,tibo66/bootstrap,SweetProcess/bootstrap,tomlutzenberger/bootstrap,realcrowd/bootstrap,TheFridayInstitute/bootstrap,igoynawamreh/bootstrap,lipis/bootstrap,sealocal/bootstrap,gijsbotje/bootstrap,creativewebjp/bootstrap,tibo66/bootstrap,joblocal/bootstrap,mpharrigan/bootstrap,yuyokk/bootstrap,m5o/bootstrap,n054/bootstrap,bardiharborow/bootstrap,frostbitten/bootstrap,wesamco/bootstrap-rtl,abvalentine/bootstrap,igoynawamreh/bootstrap,edanbarak/bootstrap,supergibbs/bootstrap,IdanCo/bootstrap,lipis/bootstrap,NCARB/bootstrap,jipexu/bootstrap,creativewebjp/bootstrap,9-chirno/chirno,vsn4ik/bootstrap,yuyokk/bootstrap,zalog/bootstrap,andresgalante/bootstrap,onenameio/rhythm-bootstrap,frostbitten/bootstrap,realcrowd/bootstrap,coliff/bootstrap,urbit/bootstrap,Delagen/bootstrap,Lyricalz/bootstrap,wesamco/bootstrap-rtl,Scoutski/bootstrap,IdanCo/bootstrap,igoynawamreh/bootstrap,peterblazejewicz/bootstrap,twbs/bootstrap,xt0rted/bootstrap,stanwmusic/bootstrap,david-schopf/bootstrap,wesamco/bootstrap-rtl,vitaligent/4,zalog/bootstrap,Hightrack/bootstrap,Hightrack/bootstrap,TheFridayInstitute/bootstrap,Lyricalz/bootstrap,sealocal/bootstrap,m5o/bootstrap,inway/bootstrap,n054/bootstrap,mpharrigan/bootstrap,zalog/bootstrap,lemuelbarango/bootstrap,janseliger/bootstrap,fschumann1211/bootstrap,sealocal/bootstrap,igoynawamreh/bootstrap,copperdesign/bootstrap,davethegr8/bootstrap,lipis/bootstrap,andresgalante/bootstrap,Hemphill/bootstrap-docs,Hemphill/bootstrap-docs,afuno/bootstrap,Scoutski/bootstrap,tjkohli/bootstrap,hellonewman81/bs4,andresgalante/bootstrap,supergibbs/bootstrap,creativewebjp/bootstrap,xt0rted/bootstrap,jipexu/bootstrap,abvalentine/bootstrap,bootstrapbrasil/bootstrap,9-chirno/chirno,blockstack/blockstack-bootstrap,bardiharborow/bootstrap,afuno/bootstrap