*: Change compatibility description for add index acceleration&PiTR

[Benjamin2037]

What is changed, added or deleted? (Required)

Add more description to make compatibility issue more clean between add index acceleration and PiTR. Let user can clearly know what will happen.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

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

• master (the latest development version)
• v6.4 (TiDB 6.4 versions)
• v6.3 (TiDB 6.3 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Oreoxmt
• tangenta

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[Oreoxmt]

@Benjamin2037 https://docs.pingcap.com/zh/tidb/dev/pitr-known-issues#%E7%B4%A2%E5%BC%95%E5%8A%A0%E9%80%9F%E5%8A%9F%E8%83%BD%E4%B8%8E-pitr-%E5%8A%9F%E8%83%BD%E4%B8%8D%E5%85%BC%E5%AE%B9 这里也需要修改

[Benjamin2037]

@Benjamin2037 https://docs.pingcap.com/zh/tidb/dev/pitr-known-issues#%E7%B4%A2%E5%BC%95%E5%8A%A0%E9%80%9F%E5%8A%9F%E8%83%BD%E4%B8%8E-pitr-%E5%8A%9F%E8%83%BD%E4%B8%8D%E5%85%BC%E5%AE%B9 这里也需要修改

这里不需要修改了，PITR 这块说明不需要修改了。

[Oreoxmt]

LGTM

[Benjamin2037]

/merge

[ti-chi-bot]

@Benjamin2037: /merge is only allowed for the committers, you can assign this pull request to the committer in list by filling /assign @committer in the comment to help merge this pull request.

In response to this:

/merge

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[shichun-0415]

LGTM

[Oreoxmt]

/merge

[ti-chi-bot]

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

Commit hash: 8ab8d6c

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #11901.