Tentative of fixing another end-to-end test

qa/qa/page/project/issue/show.rb

@@ -161,7 +161,15 @@ module QA
 
           def select_user(username)
             find("#{element_selector_css(:assignee_block)} input").set(username)
-            find('.dropdown-menu-user-link', text: "@#{username}").click
+
+            dropdown_menu_user_link_selector = '.dropdown-menu-user-link'
+            at_username = "@#{username}"
+            ten_seconds = 10
+
+            wait(reload: false, max: ten_seconds, interval: 1) do
+              has_css?(dropdown_menu_user_link_selector, wait: ten_seconds, text: at_username)
+            end
+            find(dropdown_menu_user_link_selector, text: at_username).click
           end
 
           def wait_assignees_block_finish_loading

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

 # frozen_string_literal: true
 
 module QA
-  # https://gitlab.com/gitlab-org/quality/nightly/issues/146
-  context 'Plan', :quarantine do
+  context 'Plan' do
     describe 'Multiple assignees per issue' do
       before do
         Runtime::Browser.visit(:gitlab, Page::Main::Login)
@@ -31,6 +30,8 @@ module QA
         Page::Project::Issue::Show.perform do |show|
           show.assign(@user_2)
 
+          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'