raftstore: Revert remove peer check

[tonyxuqqi]

What is changed and how it works?

Issue Number: Close #16465

What's Changed:

revert the remove peer check. Without this revert, the scale-in will be blocked when there're one slow or down peer in a region of the scale-in node. 

Related changes

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

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• LykxSassinator
• SpadeA-Tang

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[tonyxuqqi]

/merge

[ti-chi-bot]

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[ti-chi-bot]

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

Commit hash: a529349

[tonyxuqqi]

/test