Maintenance: Exclude migration tests for cherry pick branches.

.gitlab/ci/test/migration.yml

@@ -6,7 +6,7 @@
   rules:
     - if: $CI_COMMIT_REF_NAME =~ /^stable/
       when: never
-    - if: $CI_COMMIT_REF_NAME =~ /^private/
+    - if: $CI_COMMIT_REF_NAME =~ /^(private|cherry-pick-)/
       when: manual
       allow_failure: true
     - when: on_success