Update Mattermost to v10.10.2

What does this MR do and why?

This backports !8675 (merged) to 18-3-stable.

This is necessary to restore glibc < 2.34 compatibility.

See:

• https://docs.mattermost.com/product-overview/mattermost-v10-changelog.html#release-v10-10-feature-release
• #9267 (closed)
• https://github.com/mattermost/mattermost/issues/33474

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The original MR has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).