chore: enable integ test for v5/custom-clients-cognito

Author: AllanZhengYP

.circleci/config.yml

@@ -1615,6 +1615,7 @@ releasable_branches: &releasable_branches
       - release
       - main
       - next
+      - v5/custom-clients-cognito
 
 # List of test browsers that are always used in every E2E test. Tests that aren't expected to interact with browser APIs
 # should use `minimal_browser_list` to keep test execution time low.