tidb: remove experimental warnings for stats lock

[Rustin170506]

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This feature has been GAed in v7.4. But we didn't remove the warnings.

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[Rustin170506]

🔢 Self-check

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[Oreoxmt]

@hi-rustin Could you please update this file:

docs-cn/basic-features.md

Line 181 in 533821a

| [锁定统计信息](/statistics.md#锁定统计信息) | E | E | E | E | N | N | N | N | N | N | N |

@songrijie Please help confirm if we need to also update the v7.4.0 release notes here:

docs-cn/releases/release-7.4.0.md

Lines 188 to 192 in 533821a

	* 增强锁定统计信息的能力 [#46351](https://github.com/pingcap/tidb/issues/46351) @[hi-rustin](https://github.com/hi-rustin)
	在 v7.4.0 中，TiDB 增强了[锁定统计信息](/statistics.md#锁定统计信息)的能力。现在，锁定和解锁统计信息需要与收集统计信息 (`ANALYZE TABLE`) 相同的权限，以确保操作的安全性。此外，还新增了对特定分区的统计信息进行锁定和解锁操作的支持，提高了功能灵活性。当用户对数据库中的查询和执行计划有把握，并且不希望发生变化时，可以使用锁定统计信息来提升统计信息的稳定性。
	更多信息，请参考[用户文档](/statistics.md#锁定统计信息)。

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-23 06:43:24.388524235 +0000 UTC m=+598693.136147346: ☑️ agreed by Oreoxmt.
• 2024-02-26 07:30:16.618463591 +0000 UTC m=+860705.366086696: ☑️ agreed by hfxsd.

[Oreoxmt]

/approve

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.4: #16667.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #16668.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #16669.