Fix Rails/SaveBang offenses in spec/frontend

.rubocop_manual_todo.yml

@@ -151,8 +151,6 @@ Rails/SaveBang:
     - 'spec/controllers/boards/issues_controller_spec.rb'
     - 'spec/controllers/sent_notifications_controller_spec.rb'
     - 'spec/controllers/sessions_controller_spec.rb'
-    - 'spec/frontend/fixtures/issues.rb'
-    - 'spec/frontend/fixtures/merge_requests.rb'
     - 'spec/lib/after_commit_queue_spec.rb'
     - 'spec/lib/backup/manager_spec.rb'
     - 'spec/lib/gitlab/alerting/alert_spec.rb'

changelogs/unreleased/rails-save-bang-spec-frontend.yml

+---
+title: Fix Rails/SaveBang rubocop offenses in spec/frontend
+merge_request: 57909
+author: Abdul Wadood @abdulwd
+type: fixed

spec/frontend/fixtures/merge_requests.rb

@@ -69,7 +69,7 @@ RSpec.describe Projects::MergeRequestsController, '(JavaScript fixtures)', type:
   end
 
   it 'merge_requests/merge_request_of_current_user.html' do
-    merge_request.update(author: user)
+    merge_request.update!(author: user)
 
     render_merge_request(merge_request)
   end