Update registry1.dso.mil/ironbank/opensource/mattermost/mattermost Docker tag to v9.10.0

This MR contains the following updates:

Package	Update	Change
registry1.dso.mil/ironbank/opensource/mattermost/mattermost (source)	minor	9.9.1 -> 9.10.0

Complete MR checklist

Assignee

• Followed upgrade instructions outlined in docs/DEVELOPMENT_MAINTENANCE.md
• Update Docs with new/updated steps as needed
• Tested and Validated Changes made with supporting info like logs or screenshots from test pipelines

Add supporting info below

Reviewer only

• Tested and Validated changes

---

Configuration

Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

Automerge: Disabled by config. Please merge this manually once you are satisfied.

Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot

Upgrade Notices

N/A