statistics: remove useless partition stats cache

[hawkingrei]

What problem does this PR solve?

Issue Number: ref #46905

Problem Summary:

What is changed and how it works?

Check List

Tests

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

  • I checked and no code files have been changed.

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

[codecov]

Codecov Report

Merging #47201 (db6c2ea) into master (eef9f72) will decrease coverage by 0.3165%.
Report is 2 commits behind head on master.
The diff coverage is 87.5000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #47201        +/-   ##
================================================
- Coverage   72.9776%   72.6611%   -0.3165%     
================================================
  Files          1339       1360        +21     
  Lines        399847     406133      +6286     
================================================
+ Hits         291799     295101      +3302     
- Misses        89144      92258      +3114     
+ Partials      18904      18774       -130     

Flag	Coverage Δ
integration	32.3486% <62.5000%> (?)
unit	72.9698% <87.5000%> (-0.0078%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9913% <ø> (ø)
parser	84.9620% <ø> (-0.0108%)	⬇️
br	48.7321% <ø> (-4.3427%)	⬇️

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-09-22 07:41:18.98872342 +0000 UTC m=+1468.707065637: ☑️ agreed by qw4990.
• 2023-09-22 07:49:10.986060008 +0000 UTC m=+1940.704402225: ☑️ agreed by winoros.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qw4990, winoros, XuHuaiyu

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Needs approval from an approver in each of these files:

• OWNERS [XuHuaiyu,qw4990,winoros]
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