Delete bad test

This test was broken by f650e032. It was
added by https://github.com/rails/rails/pull/17978, and is adequately
tested elsewhere. The reason that this breaks is that
`Controller#process` is not going to set a new response object, and we
now terminate in callbacks if the response has been sent. The only
reason that this test was calling `get` in the first place was because
the controller under test blows up if `request` was `nil`. The point
being that the failure is invalid, and I don't think we need to fix the
test in this location.

actionview/test/actionpack/controller/render_test.rb

@@ -726,11 +726,6 @@ def test_render_in_top_directory_with_slash
     assert_equal "Elastica", @response.body
   end
 
-  def test_render_process
-    get :render_action_hello_world_as_string
-    assert_equal "Hello world!", @controller.process(:render_action_hello_world_as_string)
-  end
-
   # :ported:
   def test_render_from_variable
     get :render_hello_world_from_variable