tests/ddl: make default_as_expression test stable

[zimulala]

What problem does this PR solve?

Issue Number: close #53024

Problem Summary:

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

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, hawkingrei

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• OWNERS [Defined2014,hawkingrei]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-06 03:36:51.822321764 +0000 UTC m=+846765.579457330: ☑️ agreed by Defined2014.
• 2024-05-06 03:41:15.246064198 +0000 UTC m=+847029.003207669: ☑️ agreed by hawkingrei.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (release-8.1@a088e59). Click here to learn what that means.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #53025   +/-   ##
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  Coverage               ?   71.1231%           
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  Lines                  ?     420634           
  Branches               ?          0           
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  Hits                   ?     299168           
  Misses                 ?     100996           
  Partials               ?      20470           

Flag	Coverage Δ
unit	71.1231% <ø> (?)

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

Components	Coverage Δ
dumpling	53.9957% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	40.9827% <0.0000%> (?)