Dot release docs for server v11.4.2

[amyblais]

@claude Please prepare dot release docs for server v11.4.2.

These are the docs to update:

https://github.com/mattermost/docs/blob/master/source/deployment-guide/server/linux/deploy-rhel.rst
https://github.com/mattermost/docs/blob/master/source/deployment-guide/server/linux/deploy-tar.rst
https://github.com/mattermost/docs/blob/master/source/product-overview/mattermost-server-releases.md
https://github.com/mattermost/docs/blob/master/source/product-overview/mattermost-v11-changelog.md
https://github.com/mattermost/docs/blob/master/source/product-overview/version-archive.rst (both enterprise and team edition)

[claude]

Claude finished @amyblais's task in 4m 16s —— View job • claude/issue-8756-20260225-1459 • Create PR ➔

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Preparing dot release docs for server v11.4.2

Todo:

• Gather context and read relevant files
• Understand request (update 5 docs to replace v11.4.1 references with v11.4.2)
• Update deploy-rhel.rst with v11.4.2
• Update deploy-tar.rst with v11.4.2
• Update mattermost-server-releases.md with v11.4.2
• Update mattermost-v11-changelog.md with v11.4.2
• Update version-archive.rst (enterprise and team editions)
• Commit and push changes

All 5 files have been updated for server v11.4.2.

Note: The SHA-256 checksums in version-archive.rst are marked as TBD for the new v11.4.2 entries — please fill these in once the release artifacts are published and checksums are available. Also, please verify/update the changelog entry for 11.4.2 with the specific fixes included in this release.