[EE] Add users search results to global search

What does this MR do?

EE version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21197

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

app/helpers/projects_helper.rb

@@ -346,7 +346,8 @@ def search_tab_ability_map
       blobs:          :download_code,
       commits:        :download_code,
       merge_requests: :read_merge_request,
-      notes:          [:read_merge_request, :download_code, :read_issue, :read_project_snippet]
+      notes:          [:read_merge_request, :download_code, :read_issue, :read_project_snippet],
+      members:        :read_project_member
     )
   end