Changes

chore(pipelines/pingcap/tiflow): remove deprecated CentOS release-8.5 integration test pipelines (#3557)

Ref https://github.com/PingCAP-QE/ci/issues/3484.

Note that these pipelines were added for the urgent release of version
8.5.1 (to reuse CentOS 7 to resolve compatibility issues) and are no
longer in use.

This commit deletes several integration test pipeline scripts and their
corresponding job definitions for the release-8.5 branch, including
tests for Kafka, MySQL, Pulsar, storage, DM compatibility, DM
integration, and engine. These changes are part of the cleanup process
as these tests are no longer in use, following the removal of the CentOS
8.5 pipelines.

Additionally, the related configuration in the kustomization.yaml file
has been updated to reflect these deletions.
 (commit: 34f2405)