Revert "Remove ruby-head from allow_failures matrix"
Revert "Remove ruby-head from allow_failures matrix"

This reverts commit 5d2d301024cc0b17f26f6b454ac22a72f1db8a23.

Erol/rails,ttanimichi/rails,Stellenticket/rails,MSP-Greg/rails,lcreid/rails,fabianoleittes/rails,starknx/rails,Erol/rails,illacceptanything/illacceptanything,MichaelSp/rails,aditya-kapoor/rails,bogdanvlviv/rails,BlakeWilliams/rails,gauravtiwari/rails,jeremy/rails,elfassy/rails,tijwelch/rails,rafaelfranca/omg-rails,riseshia/railsguides.kr,gavingmiller/rails,mathieujobin/reduced-rails-for-travis,kenta-s/rails,Edouard-chin/rails,rbhitchcock/rails,utilum/rails,kmcphillips/rails,gfvcastro/rails,richseviora/rails,mijoharas/rails,tgxworld/rails,georgeclaghorn/rails,Envek/rails,alecspopa/rails,MSP-Greg/rails,tgxworld/rails,stefanmb/rails,illacceptanything/illacceptanything,baerjam/rails,sealocal/rails,arjes/rails,arunagw/rails,xlymian/rails,voray/rails,vipulnsward/rails,georgeclaghorn/rails,lcreid/rails,printercu/rails,yasslab/railsguides.jp,kirs/rails-1,pvalena/rails,mohitnatoo/rails,kenta-s/rails,pschambacher/rails,notapatch/rails,maicher/rails,iainbeeston/rails,yhirano55/rails,EmmaB/rails-1,tjschuck/rails,Spin42/rails,pvalena/rails,georgeclaghorn/rails,voray/rails,samphilipd/rails,elfassy/rails,arunagw/rails,untidy-hair/rails,samphilipd/rails,yahonda/rails,schuetzm/rails,assain/rails,bogdanvlviv/rails,fabianoleittes/rails,betesh/rails,koic/rails,mtsmfm/rails,hanystudy/rails,kaspth/rails,schuetzm/rails,arunagw/rails,odedniv/rails,mtsmfm/rails,vipulnsward/rails,rbhitchcock/rails,bradleypriest/rails,gcourtemanche/rails,matrinox/rails,gauravtiwari/rails,bolek/rails,mtsmfm/rails,Vasfed/rails,EmmaB/rails-1,kmcphillips/rails,gfvcastro/rails,fabianoleittes/rails,prathamesh-sonpatki/rails,kachick/rails,bolek/rails,mechanicles/rails,vipulnsward/rails,Vasfed/rails,tjschuck/rails,palkan/rails,ngpestelos/rails,repinel/rails,shioyama/rails,koic/rails,BlakeWilliams/rails,rbhitchcock/rails,Envek/rails,MichaelSp/rails,MichaelSp/rails,kmcphillips/rails,88rabbit/newRails,yawboakye/rails,printercu/rails,matrinox/rails,riseshia/railsguides.kr,kaspth/rails,88rabbit/newRails,sergey-alekseev/rails,esparta/rails,palkan/rails,vassilevsky/rails,gfvcastro/rails,ledestin/rails,yahonda/rails,amoody2108/TechForJustice,amoody2108/TechForJustice,joonyou/rails,BlakeWilliams/rails,travisofthenorth/rails,MSP-Greg/rails,sergey-alekseev/rails,maicher/rails,yhirano55/rails,printercu/rails,Spin42/rails,88rabbit/newRails,illacceptanything/illacceptanything,Envek/rails,eileencodes/rails,mechanicles/rails,yalab/rails,ngpestelos/rails,brchristian/rails,Edouard-chin/rails,kddeisz/rails,coreyward/rails,baerjam/rails,brchristian/rails,kmayer/rails,felipecvo/rails,untidy-hair/rails,kddeisz/rails,jeremy/rails,illacceptanything/illacceptanything,betesh/rails,flanger001/rails,mtsmfm/railstest,kmayer/rails,gcourtemanche/rails,kenta-s/rails,koic/rails,Stellenticket/rails,richseviora/rails,aditya-kapoor/rails,repinel/rails,utilum/rails,tjschuck/rails,BlakeWilliams/rails,deraru/rails,baerjam/rails,starknx/rails,prathamesh-sonpatki/rails,joonyou/rails,gauravtiwari/rails,arjes/rails,ledestin/rails,amoody2108/TechForJustice,palkan/rails,richseviora/rails,vassilevsky/rails,prathamesh-sonpatki/rails,schuetzm/rails,odedniv/rails,coreyward/rails,mohitnatoo/rails,lcreid/rails,rossta/rails,felipecvo/rails,tijwelch/rails,vassilevsky/rails,illacceptanything/illacceptanything,mechanicles/rails,riseshia/railsguides.kr,yawboakye/rails,Vasfed/rails,Sen-Zhang/rails,Envek/rails,prathamesh-sonpatki/rails,illacceptanything/illacceptanything,pschambacher/rails,mtsmfm/railstest,yawboakye/rails,esparta/rails,bogdanvlviv/rails,ngpestelos/rails,deraru/rails,esparta/rails,georgeclaghorn/rails,ttanimichi/rails,sergey-alekseev/rails,mohitnatoo/rails,mathieujobin/reduced-rails-for-travis,kmayer/rails,utilum/rails,alecspopa/rails,mijoharas/rails,joonyou/rails,shioyama/rails,gcourtemanche/rails,yasslab/railsguides.jp,EmmaB/rails-1,yawboakye/rails,tjschuck/rails,assain/rails,hanystudy/rails,mijoharas/rails,marklocklear/rails,kddeisz/rails,starknx/rails,yasslab/railsguides.jp,repinel/rails,hanystudy/rails,kamipo/rails,eileencodes/rails,Sen-Zhang/rails,ledestin/rails,brchristian/rails,betesh/rails,jeremy/rails,illacceptanything/illacceptanything,palkan/rails,joonyou/rails,illacceptanything/illacceptanything,aditya-kapoor/rails,jeremy/rails,xlymian/rails,tgxworld/rails,gavingmiller/rails,yahonda/rails,kmcphillips/rails,shioyama/rails,Edouard-chin/rails,shioyama/rails,matrinox/rails,xlymian/rails,yalab/rails,pvalena/rails,kirs/rails-1,rails/rails,untidy-hair/rails,vipulnsward/rails,Spin42/rails,lucasmazza/rails,kamipo/rails,yahonda/rails,assain/rails,mtsmfm/railstest,lcreid/rails,flanger001/rails,rafaelfranca/omg-rails,iainbeeston/rails,MSP-Greg/rails,bolek/rails,flanger001/rails,kaspth/rails,bogdanvlviv/rails,yalab/rails,maicher/rails,Sen-Zhang/rails,iainbeeston/rails,assain/rails,Erol/rails,Stellenticket/rails,printercu/rails,Edouard-chin/rails,arjes/rails,marklocklear/rails,stefanmb/rails,betesh/rails,flanger001/rails,marklocklear/rails,iainbeeston/rails,gfvcastro/rails,illacceptanything/illaccept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