flaky test `pkg/disttask/framework/storage/storage_test_/storage_test_shard_21/25`

[lance6716]

Bug Report

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1. Minimal reproduce step (Required)

I meet them often. Like https://do.pingcap.net/jenkins/blue/organizations/jenkins/pingcap%2Ftidb%2Fghpr_unit_test/detail/ghpr_unit_test/33993/tests

It's timed out finally

-- Test timed out at 2025-06-03 06:01:16 UTC --

Maybe this test case is too slow

�--- PASS: TestTaskManagerEntrySize (145.60s)

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

[D3Hunter]

see #60239 (comment)