statistics: fix two unstable tests

[rebelice]

What problem does this PR solve?

Issue Number: close #24679, close #24010

Problem Summary:

What is changed and how it works?

Proposal: xxx

What's Changed:

How it Works:

It's a random test, skip race test

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

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

Side effects

• Performance regression
  • Consumes more CPU
  • Consumes more MEM
• Breaking backward compatibility

Release note

• No release note

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[qw4990]

/merge

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/merge

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[qw4990]

@zhuo-zhi Please help us review it.

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• qw4990
• zhuo-zhi

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[qw4990]

/merge

[ti-chi-bot]

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

Commit hash: 2ab8c27