Update testing guide to reflect changes from #36047
Update testing guide to reflect changes from #36047

In #36047 we moved `take_failed_screenshot` from an `after_teardown`
hook to a `before_teardown` hook. However, I didn't realize the Testing
rails guide was explicitly mentioning that it happened inside
`after_teardown`. So this updates the docs to be consistent with that
change.

[ci skip]

shioyama/rails,georgeclaghorn/rails,jeremy/rails,yhirano55/rails,betesh/rails,jeremy/rails,joonyou/rails,joonyou/rails,iainbeeston/rails,Edouard-chin/rails,mechanicles/rails,schuetzm/rails,BlakeWilliams/rails,esparta/rails,starknx/rails,jeremy/rails,tjschuck/rails,gauravtiwari/rails,schuetzm/rails,lcreid/rails,fabianoleittes/rails,mechanicles/rails,prathamesh-sonpatki/rails,repinel/rails,tjschuck/rails,arunagw/rails,Stellenticket/rails,tgxworld/rails,kmcphillips/rails,gauravtiwari/rails,Stellenticket/rails,arunagw/rails,mechanicles/rails,iainbeeston/rails,eileencodes/rails,Vasfed/rails,vipulnsward/rails,palkan/rails,tjschuck/rails,palkan/rails,rails/rails,kmcphillips/rails,joonyou/rails,gauravtiwari/rails,rafaelfranca/omg-rails,rails/rails,flanger001/rails,BlakeWilliams/rails,tjschuck/rails,yahonda/rails,yawboakye/rails,Stellenticket/rails,schuetzm/rails,eileencodes/rails,Edouard-chin/rails,yawboakye/rails,mechanicles/rails,vipulnsward/rails,shioyama/rails,yalab/rails,kddeisz/rails,yawboakye/rails,georgeclaghorn/rails,flanger001/rails,flanger001/rails,Vasfed/rails,BlakeWilliams/rails,yhirano55/rails,yalab/rails,yhirano55/rails,fabianoleittes/rails,iainbeeston/rails,betesh/rails,Erol/rails,lcreid/rails,bogdanvlviv/rails,bogdanvlviv/rails,MSP-Greg/rails,Edouard-chin/rails,notapatch/rails,rafaelfranca/omg-rails,MSP-Greg/rails,fabianoleittes/rails,Envek/rails,notapatch/rails,starknx/rails,MSP-Greg/rails,betesh/rails,schuetzm/rails,Erol/rails,arunagw/rails,Erol/rails,kmcphillips/rails,EmmaB/rails-1,repinel/rails,palkan/rails,prathamesh-sonpatki/rails,MSP-Greg/rails,kmcphillips/rails,prathamesh-sonpatki/rails,EmmaB/rails-1,vipulnsward/rails,lcreid/rails,arunagw/rails,kddeisz/rails,esparta/rails,flanger001/rails,rails/rails,eileencodes/rails,Envek/rails,fabianoleittes/rails,esparta/rails,rafaelfranca/omg-rails,kddeisz/rails,georgeclaghorn/rails,shioyama/rails,shioyama/rails,prathamesh-sonpatki/rails,BlakeWilliams/rails,yalab/rails,Envek/rails,yhirano55/rails,repinel/rails,yahonda/rails,Edouard-chin/rails,bogdanvlviv/rails,kddeisz/rails,betesh/rails,tgxworld/rails,eileencodes/rails,yalab/rails,notapatch/rails,tgxworld/rails,yahonda/rails,notapatch/rails,EmmaB/rails-1,yawboakye/rails,rails/rails,georgeclaghorn/rails,jeremy/rails,Envek/rails,palkan/rails,joonyou/rails,bogdanvlviv/rails,repinel/rails,vipulnsward/rails,esparta/rails,yahonda/rails,tgxworld/rails,Vasfed/rails,starknx/rails,Stellenticket/rails,Vasfed/rails,Erol/rails,lcreid/rails,iainbeeston/rails