Remove mention to deprecated Heroku pgbackups addon
Remove mention to deprecated Heroku pgbackups addon

https://devcenter.heroku.com/changelog-items/623

[fixes #577]

delphaber/suspenders,mukkoo/welaika-suspenders,pacso/suspenders,headwayio/voyage,kvokka/suspenders,zamith/suspenders,Mossio/hashira-rails,pacso/suspenders,adarsh/suspenders,mico/suspenders,lorentrogers/suspenders,kvokka/suspenders,Mossio/hashira-rails,askl56/suspenders,wizarddevelopment/bowties,kvokka/suspenders,cybrilla/suspenders,InnovativeOperations/suspenders,thoughtbot/suspenders,headwayio/suspenders,Mossio/hashira-rails,namuit/welaika-suspenders,elevatorup/eu-suspenders,lorentrogers/suspenders,Mario245/suspenders,namuit/welaika-suspenders,headwayio/suspenders,cybrilla/suspenders,brandoncordell/suspenders,thoughtbot/suspenders,pineapplethief/suspenders,mukkoo/welaika-suspenders,elevatorup/eu-suspenders,delphaber/suspenders,toobulkeh/suspenders,headwayio/voyage,nplusp/suspenders,pacso/suspenders,welaika/welaika-suspenders,askl56/suspenders,nplusp/suspenders,nilbus/suspenders,brandoncordell/suspenders,mib32/suspenders,adarsh/suspenders,Mossio/hashira-rails,mib32/suspenders,Mario245/suspenders,InnovativeOperations/suspenders,wizarddevelopment/bowties,welaika/welaika-suspenders,lorentrogers/suspenders,elevatorup/eu-suspenders,headwayio/voyage,nilbus/suspenders,cybrilla/suspenders,elijahkim/suspenders,InnovativeOperations/suspenders,mukkoo/welaika-suspenders,thoughtbot/suspenders,toobulkeh/suspenders,zamith/suspenders,namuit/welaika-suspenders,elijahkim/suspenders,Mario245/suspenders,mico/suspenders,nilbus/suspenders,askl56/suspenders,adarsh/suspenders,pineapplethief/suspenders,mib32/suspenders,welaika/welaika-suspenders,brandoncordell/suspenders,pedrosmmoreira/suspenders,pedrosmmoreira/suspenders,headwayio/voyage,nplusp/suspenders,delphaber/suspenders,headwayio/suspenders,zamith/suspenders,toobulkeh/suspenders,pineapplethief/suspenders,wizarddevelopment/bowties,elijahkim/suspenders,pedrosmmoreira/suspenders,headwayio/suspenders,mico/suspenders