Fix a typo in the code of Testing guide.
Fix a typo in the code of Testing guide.

Replace the word «Accepts» by «Accept» in the example of custom request headers.

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