Update a test to avoid flakiness

This test has shown failures when running on CI, because automatic
comments sometimes do not show up, but with the two other expecta-
tions, we can still test that the functionality of assigning mul-
tiple users to an issue works.

So, better having one less expectation, but having reliable test
results, than having an extra expectation that leads to a flaky
test and false negatives.

qa/qa/specs/features/ee/browser_ui/2_plan/multiple_assignees_for_issues/two_assignees_spec.rb

@@ -31,7 +31,6 @@ module QA
 
           show.select_all_activities_filter
 
-          expect(show).to have_content "assigned to @#{@user_2.username}"
           expect(show.avatar_image_count).to be 2
           expect(show.assignee_title).to have_content '2 Assignees'
         end