basic features: fix anchor link

[Oreoxmt]

What is changed, added or deleted? (Required)

Update the link for invisible indexes to point correctly from /sql-statements/sql-statement-add-index.md to /sql-statements/sql-statement-create-index.md#invisible-index.

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

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• v8.0 (TiDB 8.0 versions)
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• 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: basic features: fix anchor link docs-cn#16973
• 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

[lilin90]

/lgtm

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-02 06:21:58.353398705 +0000 UTC m=+338579.880939252: ☑️ agreed by hfxsd.
• 2024-04-02 06:22:43.369284364 +0000 UTC m=+338624.896824910: ☑️ agreed by lilin90.

[Oreoxmt]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #16925.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.4: #16926.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #16927.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #16928.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #16929.