build(deps): bump mattermost/action-mattermost-notify

Bumps [mattermost/action-mattermost-notify](https://github.com/mattermost/action-mattermost-notify) from 1.1.0 to 2.0.0.
- [Release notes](https://github.com/mattermost/action-mattermost-notify/releases)
- [Commits](mattermost/action-mattermost-notify@1.1.0...2.0.0)

---
updated-dependencies:
- dependency-name: mattermost/action-mattermost-notify
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/mattermost.yml

@@ -13,6 +13,6 @@ jobs:
         run: >
           jq -n --arg t "Pull request opened: [${TITLE}](${HTML_LINK})" '{text: $t}'
           > mattermost.json
-      - uses: mattermost/action-mattermost-notify@1.1.0
+      - uses: mattermost/action-mattermost-notify@2.0.0
         env:
           MATTERMOST_WEBHOOK_URL: ${{ secrets.MATTERMOST_WEBHOOK_URL }}