GH-28752 fix errcheck lint issues in server/channels/testlib/helper.go (#29260)

server/.golangci.yml

@@ -203,7 +203,6 @@ issues:
         channels/store/storetest/team_store.go|\
         channels/store/storetest/thread_store.go|\
         channels/store/storetest/user_store.go|\
-        channels/testlib/helper.go|\
         channels/utils/license_test.go|\
         channels/web/oauth_test.go|\
         channels/web/saml.go|\