Remove extra assertions from end-to-end test

By asserting that the epic title is the same of the issue that
was promoted we are already testing that issue promotion works, so
better to remove this extra assertions that might cause test flaki-
ness since sometimes automatic discussions take longer to render.

Also, by removing an extra step + assertion, we make the test a bit
faster.

Finally, this way the code gets a bit shorter.

qa/qa/specs/features/ee/browser_ui/2_plan/epic/promote_issue_to_epic_spec.rb

@@ -39,12 +39,7 @@ module QA
         Page::Group::Menu.perform(&:click_group_epics_link)
         QA::EE::Page::Group::Epic::Index.perform do |index|
           expect(index).to have_epic_title(issue_title)
-
-          index.click_first_epic(QA::EE::Page::Group::Epic::Show)
         end
-
-        expect(page).to have_content(issue_title)
-        expect(page).to have_content(/promoted from issue .* \(closed\)/)
       end
     end
   end