Remove duplicated Contribution Graph spec

We have the spec duplicated for both beta and non-beta version of the
code.

The non-beta one is causing flickering tests in our CI. Since nobody
sees the non-beta version of the UI anymore and the feature flag is
going to be removed in a few days, we decide to remove the non-beta spec.

src/api/spec/features/beta/webui/users/user_contributions_spec.rb

@@ -1,3 +1,6 @@
+# TODO: move this test out of the beta directory as soon as the
+# user_profile_redesign feature flag is removed.
+
 require 'browser_helper'
 
 RSpec.shared_examples 'a contribution graph' do
@@ -61,6 +64,8 @@
         click_link('Contributions')
         expect(page).to have_text('3 contributions')
       end
+
+      # TODO: test single day contributions by clicking on a percentil and check the resulting text.
     end
   end
 end