TiFlash: Fix incorrect values of isolation_read_engines

[shichun-0415]

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This PR is to fix #9574

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[windtalker]

LGTM

[shichun-0415]

/remove status LGT1
/status LGT2

[shichun-0415]

/merge

[ti-chi-bot]

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

Commit hash: 781919c

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9578.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9579.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9580.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9581.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9582.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9583.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #9584.