Migrate runner_setup_controller_spec.rb to request spec

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

changelogs/unreleased/epic-5076-spec-controllers-runner_setup_controller_spec-rb.yml

+---
+title: Migrate runner_setup_controller_spec.rb to request spec
+merge_request: 50600
+author: Takuya Noguchi
+type: other

spec/controllers/runner_setup_controller_spec.rb → spec/requests/runner_setup_controller_spec.rb

@@ -9,9 +9,9 @@ RSpec.describe RunnerSetupController do
     sign_in(user)
   end
 
-  describe 'GET #platforms' do
+  describe 'GET /-/runner_setup/platforms' do
     it 'renders the platforms' do
-      get :platforms
+      get runner_setup_platforms_url
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response).to have_key("windows")