Changes

fix(pipelines/pingcap-qe/tidb-test): fix pipelines (#3654)

This pull request includes updates to the pipeline configuration for
testing in the `tidb-test` project. The changes focus on improving
caching, modifying test configurations, and cleaning up the pipeline
scripts.

### Caching improvements:
* Updated the cache key in the `pull_integration_jdbc_test_next_gen`
pipeline to use a workspace-specific key format
(`ws/${BUILD_TAG}/tidb-test`) for better cache management.
(`[pipelines/pingcap-qe/tidb-test/latest/pull_integration_jdbc_test_next_gen/pipeline.groovyL137-R137](diffhunk://#diff-eea030b5a2abb8b2e5e3a1be2362ce7712fc41dd2b252430b51432f9d9663366L137-R137)`)

### Test configuration changes:
* Modified the `STORE` axis in the `pull_mysql_test_next_gen` pipeline
to temporarily exclude `tikv` from the list of values.
(`[pipelines/pingcap-qe/tidb-test/latest/pull_mysql_test_next_gen/pipeline.groovyL88-R87](diffhunk://#diff-7c278a7e52ae6c08b00ca70ee8f001a39c9c3cdd1a3c6570aebe98fe4e1a08b9L88-R87)`)
* Removed the timeout option from the `Test` stage in the
`pull_mysql_test_next_gen` pipeline, potentially allowing tests to run
without a time limit.
(`[pipelines/pingcap-qe/tidb-test/latest/pull_mysql_test_next_gen/pipeline.groovyL100](diffhunk://#diff-7c278a7e52ae6c08b00ca70ee8f001a39c9c3cdd1a3c6570aebe98fe4e1a08b9L100)`)

### Code cleanup:
* Removed an outdated comment about triggering conditions in the
`pull_mysql_test_next_gen` pipeline.
(`[pipelines/pingcap-qe/tidb-test/latest/pull_mysql_test_next_gen/pipeline.groovyL3](diffhunk://#diff-7c278a7e52ae6c08b00ca70ee8f001a39c9c3cdd1a3c6570aebe98fe4e1a08b9L3)`)
 (commit: dcdce0d)