Use `updatedBy` to show test case edit info

Adds `updatedBy` connection to show edited
by author name in test cases.

ee/app/assets/javascripts/test_case_show/queries/test_case.fragment.graphql

@@ -10,6 +10,9 @@ fragment TestCase on Issue {
   state
   createdAt
   updatedAt
+  updatedBy {
+    ...Author
+  }
   webUrl
   blocked
   confidential

ee/spec/features/projects/quality/test_case_show_spec.rb

@@ -89,7 +89,7 @@ RSpec.describe 'Test Cases', :js do
         page.within('.test-case-container .issuable-details') do
           expect(page.find('.title')).to have_content(title)
           expect(page.find('.description')).to have_content(description)
-          expect(page.find('.edited-text')).to have_content('')
+          expect(page.find('.edited-text')).to have_content("Edited just now by #{user.name}")
         end
       end
     end