update aliases for release-8.1 branch

[Oreoxmt]

What is changed, added or deleted? (Required)

• Remove all aliases for v8.1
• Add aliases for sql-statements/sql-statement-show-histograms.md (ref ebnf show stats_histograms #17051) and ddl-v2.md (ref rename tidb_ddl_version to tidb_enable_fast_create_table #16789)

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

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v8.1 (TiDB 8.1 versions)
• v8.0 (TiDB 8.0 versions)
• v7.6 (TiDB 7.6 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 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)

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

• This PR is translated from: update aliases for release-8.1 branch docs-cn#17346
• 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:

• 2024-05-16 04:18:47.020634277 +0000 UTC m=+1713280.777769843: ☑️ agreed by lilin90.

[Oreoxmt]

/approve

[ti-chi-bot]

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