errors: fix wrong usage of ErrClientGetTSO

[CabinfeverB]

What problem does this PR solve?

Issue Number: ref #7496

What is changed and how does it work?

Check List

Tests

• Manual test (add detailed scripts or steps below)
  before
  

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• HuSharp
• JmPotato

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[codecov]

Codecov Report

Merging #7865 (33851e8) into master (2e3e4c0) will not change coverage.
The diff coverage is 50.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7865   +/-   ##
=======================================
  Coverage   73.49%   73.49%           
=======================================
  Files         432      432           
  Lines       47958    47958           
=======================================
  Hits        35245    35245           
- Misses       9667     9671    +4     
+ Partials     3046     3042    -4     

Flag	Coverage Δ
unittests	73.49% <50.00%> (ø)

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[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 33851e8