ttl: fix unstable test 'TestTTLTimerHookOnEvent'

[lcwangchao]

What problem does this PR solve?

Issue Number: close #45445

What is changed and how it works?

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

[hawkingrei]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, YangKeao

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• OWNERS [YangKeao,hawkingrei]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-07-18 10:22:37.580315432 +0000 UTC m=+1018649.350654130: ☑️ agreed by hawkingrei.
• 2023-07-19 03:04:39.687788837 +0000 UTC m=+1078771.458127549: ☑️ agreed by YangKeao.

[codecov]

Codecov Report

Merging #45446 (3dafbe5) into master (49bdaaf) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff             @@
##             master     #45446   +/-   ##
===========================================
  Coverage   73.2552%   73.2552%           
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  Files          1261       1261           
  Lines        388873     388873           
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  Hits         284870     284870           
- Misses        85748      85749    +1     
+ Partials      18255      18254    -1     

Flag	Coverage Δ
unit	73.2552% <ø> (ø)

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Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0899% <ø> (ø)
br	52.0952% <ø> (ø)