Changes

ticdc: Enable `skip_if_only_changed` for next-gen presubmit jobs (#3868)

This pull request addresses an issue where the `skip_if_only_changed`
directive was commented out in several Prow jobs for the `pingcap/ticdc`
repository.

The changes in this pull request include:

* Uncommenting the `skip_if_only_changed: *skip_if_only_changed`
directive for the following Prow jobs:
  * `pingcap/ticdc/pull_cdc_mysql_integration_light_next_gen`
  * `pull-unit-test-next-gen`
  * `pull-build-next-gen`

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Signed-off-by: tenfyzhong <tenfy@tenfy.cn>
 (commit: 407aec9)