Specfix: expect only on the explicit flash-message

Previous test-data used a blob of text in multiple tags and was too brittle.

Author: rud

spec/acceptance/sign_in_with_google_spec.rb

@@ -59,6 +59,6 @@
     mock_auth('unknown_but_invalid_user')
 
     click_link 'Sign in with Google'
-    expect(page).to have_content "Sign in with GitHub Sign in with Google Account's email domain is not authorized for login. Please log in with an account from a trusted domain."
+    expect(page).to have_text I18n.t('devise.google_login.domain_unauthorized')
   end
 end