fix(tests): Update the submit button selector for the permissions screen tests.
fix(tests): Update the submit button selector for the permissions screen tests.

The old selector was `#accept`, the new selector is `#proceed`.

fixes #2462

swatilk/fxa-content-server,dannycoates/fxa-content-server,shane-tomlinson/fxa-content-server,swatilk/fxa-content-server,mozilla/fxa-content-server,shane-tomlinson/fxa-content-server,riadhchtara/fxa-password-manager,swatilk/fxa-content-server,riadhchtara/fxa-password-manager,riadhchtara/fxa-content-server,riadhchtara/fxa-content-server,riadhchtara/fxa-password-manager,ReachingOut/fxa-content-server,TDA/fxa-content-server,shane-tomlinson/fxa-content-server,npestana/fxa-content-server,dannycoates/fxa-content-server,atiqueahmedziad/fxa-content-server,chilts/fxa-content-server,ofer43211/fxa-content-server,ofer43211/fxa-content-server,mozilla/fxa-content-server,vladikoff/fxa-content-server,TDA/fxa-two-factor-auth,npestana/fxa-content-server,dannycoates/fxa-content-server,npestana/fxa-content-server,ReachingOut/fxa-content-server,chilts/fxa-content-server,vladikoff/fxa-content-server,ReachingOut/fxa-content-server,riadhchtara/fxa-content-server,chilts/fxa-content-server,TDA/fxa-content-server,atiqueahmedziad/fxa-content-server,mozilla/fxa-content-server,vladikoff/fxa-content-server,atiqueahmedziad/fxa-content-server,TDA/fxa-content-server,ofer43211/fxa-content-server,TDA/fxa-two-factor-auth,TDA/fxa-two-factor-auth