Merge branch '58969-fix-request-context-spec' into 'master'

Fix test environment pollution in spec/lib/gitlab/request_context_spec.rb

Closes #58969

See merge request gitlab-org/gitlab-ce!26167

spec/lib/gitlab/request_context_spec.rb

@@ -25,7 +25,7 @@
           [200, {}, ["Hello"]]
         end
 
-        Rails.application.middleware.build(endpoint).call(env)
+        described_class.new(endpoint).call(env)
 
         expect(client_ip).to eq(load_balancer_ip)
       end