tidb: fix default value of performance.committer-concurrency

[amyangfei]

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What is changed, added or deleted? (Required)

The default value of performance.committer-concurrency has changed from 16 to 128 since v5.1.0

ref: https://docs.pingcap.com/zh/tidb/dev/release-5.1.0#%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E5%8F%82%E6%95%B0 performance.committer-concurrency

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For details, see tips for choosing the affected versions (in Chinese).

• master (the latest development version)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

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• Delete files
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• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

[ti-chi-bot]

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

Commit hash: 5469353

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7120.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7121.