br: fix br integration test 7.1.1 (#50740)

[ti-chi-bot]

This is an automated cherry-pick of #50740

What problem does this PR solve?

Issue Number: close #50741

Problem Summary:
br integration test bug

What changed and how does it work?

fix br integration test: match the correct error string

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

[Leavrth]

/test pull-br-integration-test

[tiprow]

@Leavrth: No presubmit jobs available for pingcap/tidb@release-7.1

In response to this:

/test pull-br-integration-test

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@503bf72). Click here to learn what that means.
The diff coverage is 100.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #51438   +/-   ##
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  Coverage               ?   73.4245%           
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  Files                  ?       1212           
  Lines                  ?     379474           
  Branches               ?          0           
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  Hits                   ?     278627           
  Misses                 ?      83057           
  Partials               ?      17790           

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BornChanger, YuJuncen

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• OWNERS [YuJuncen]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-03-01 02:10:00.15522622 +0000 UTC m=+1187088.902849333: ☑️ agreed by BornChanger.
• 2024-03-01 02:39:12.480452251 +0000 UTC m=+1188841.228075377: ☑️ agreed by YuJuncen.