*: fix broken links

[Oreoxmt]

What is changed, added or deleted? (Required)

Fix broken links:

• The link to the node-mysql2 documentation has been updated. The previous URL https://github.com/sidorares/node-mysql2/tree/master/documentation/en was removed in chore: remove duplicate documentation and examples sidorares/node-mysql2#2326. It now points to the current documentation site: https://sidorares.github.io/node-mysql2/docs/documentation.
• The link https://docs.pingcap.com/tidb/stable/dev-guide-sample-application-java is leading to a 404 error because develop/dev-guide-sample-application-java.md was removed without any redirect aliases being added.
• The TiDB Lightning package https://github.com/pingcap/tidb/tree/master/br/pkg/lightning was modified to https://github.com/pingcap/tidb/tree/master/lightning in lightning: move lightning directory out of br tidb#52247.

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)
• v7.4 (TiDB 7.4 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: *: fix broken links docs-cn#17030
• 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

[Oreoxmt]

@D3Hunter Please review a8f2e2a

[Oreoxmt]

/cc @lilin90

[D3Hunter]

lightning part lgtm

[ti-chi-bot]

@D3Hunter: adding LGTM is restricted to approvers and reviewers in OWNERS files.

In response to this:

lightning part lgtm

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[lilin90]

/lgtm

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-09 05:52:06.483761134 +0000 UTC m=+941588.011301675: ☑️ agreed by lilin90.

[lilin90]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lilin90

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• OWNERS [lilin90]

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #17062.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #17063.