ddl: unlock schema version mutex properly

[tangenta]

What problem does this PR solve?

Issue Number: close #50309

Problem Summary: #50251 missed one line.

What changed and how does it work?

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

[tiprow]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-11 08:30:16.148912355 +0000 UTC m=+518405.733166038: ☑️ agreed by ywqzzy.
• 2024-01-11 08:31:31.393697718 +0000 UTC m=+518480.977951405: ☑️ agreed by hawkingrei.

[hawkingrei]

/check-issue-triage-complete

[codecov]

Codecov Report

Merging #50327 (4d94063) into master (0236944) will decrease coverage by 14.6068%.
Report is 3 commits behind head on master.
The diff coverage is 100.0000%.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #50327         +/-   ##
=================================================
- Coverage   69.9866%   55.3799%   -14.6068%     
=================================================
  Files          1444       1555        +111     
  Lines        419930     586855     +166925     
=================================================
+ Hits         293895     325000      +31105     
- Misses       105704     239152     +133448     
- Partials      20331      22703       +2372     

Flag	Coverage Δ
integration	36.5579% <0.0000%> (?)
unit	69.9962% <100.0000%> (+0.0096%)	⬆️

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

Components	Coverage Δ
dumpling	54.0269% <ø> (ø)
parser	∅ <ø> (∅)
br	55.5216% <ø> (+5.8707%)	⬆️

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, ywqzzy, zimulala

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• pkg/ddl/OWNERS [ywqzzy,zimulala]

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[hawkingrei]

/retest