Changes

Revert "feat(br): enable condition trigger of br test on 8.1" (#3367)

Reverts PingCAP-QE/ci#3332

Some br tests have failed; automatic triggering will be enabled after
the tests are fixed.

test link:
1.
https://do.pingcap.net/jenkins/blue/organizations/jenkins/pingcap%2Ftidb%2Frelease-8.1%2Fpull_br_integration_test/detail/pull_br_integration_test/29/pipeline/241
<img width="338" alt="image"
src="https://github.com/user-attachments/assets/3d0f8a9a-c030-4bfa-9e6f-00197d117465"
/>
 (commit: 349a986)