Update user_cas_omniauth_authorize_path request to be post

Co-authored-by: Jane Sandberg <[email protected]>

spec/requests/users_request_spec.rb

@@ -33,7 +33,7 @@
         )
         allow(User).to receive(:from_omniauth).and_return(user)
 
-        get user_cas_omniauth_authorize_path
+        post user_cas_omniauth_authorize_path
       end
 
       after do