Remove duplicate docs for SHOW INDEX, SHOW KEYS infavor of SHOW INDEXES

[enkilee]

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fix #pingcap/docs#15364

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

• This PR is translated from: Remove duplicate docs for SHOW INDEX, SHOW KEYS in favor of SHOW INDEXES docs#15364
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Do your changes match any of the following descriptions?

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

[ran-huang]

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[ran-huang]

Rest LGTM

[ran-huang]

The rest LGTM, but the file sql-statements/sql-statement-rename-index.md is not modified the same way as in the English PR.

[enkilee]

The rest LGTM, but the file sql-statements/sql-statement-rename-index.md is not modified the same way as in the English PR.

sorry. fix it.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-15 03:34:48.385527399 +0000 UTC m=+154129.949825104: ☑️ agreed by ran-huang.
• 2024-01-16 03:15:20.317669276 +0000 UTC m=+239361.881966981: ✖️🔁 reset by ran-huang.
• 2024-01-24 04:26:58.254011814 +0000 UTC m=+934859.818309504: ☑️ agreed by ran-huang.

[ran-huang]

/approve

[ti-chi-bot]

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This pull-request has been approved by: ran-huang

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #16277.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.3: #16279.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.4: #16281.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #16282.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #16283.