refactor(tiflow): move cdc integration scope filters to prow (#4337)
## Summary - move the tiflow `pull_cdc_integration_*` change-scope gate from duplicated Jenkins pipeline logic into Prow `skip_if_only_changed` filters across active branches - remove the `Check diff files` stage and related skip plumbing from the affected tiflow CDC integration pipelines - rename the shared Prow anchor to `skip_if_only_changed_non_ticdc_files` so its intent is clearer to contributors
## Validation - run `.ci/update-prow-job-kustomization.sh` - run `JENKINS_URL=https://do.pingcap.net/jenkins .ci/verify-jenkins-pipelines.sh` - run `git diff --check` (commit: c881355)