tools/check: 'ut' now remove support for the old test cases

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #30822

Problem Summary:

Since the test case migration is done #26022, we can now remove the support for the old test case.

What is changed and how it works?

Address comment here #30822 (comment)

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hawkingrei
• tisonkun

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[tisonkun]

LGTM. Although, I'm unsure whether this pr completely "closes" #30822.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/a32f425b137048d3355689aecf3740173e154e67

[hawkingrei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 11025b7

[tisonkun]

/run-mysql-test

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! [1] CI still failing after this pr merged.
These failed integration tests don't seem to be introduced by the current PR.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci/integration-cdc-test	🔴 failed 1, success 33, total 34	30 min	Existing failure
idc-jenkins-ci-tidb/integration-common-test	🟢 all 11 tests passed	21 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	8 min 25 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	7 min 53 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	7 min 32 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 43 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 36 sec	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	6 min 34 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	5 min 55 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed