ci: pin action-mattermost-notify to v2.0.0 SHA (security)

Author: anneschuth

.github/workflows/ci.yml

@@ -293,7 +293,7 @@ jobs:
       ]
     if: ${{ always() && contains(needs.*.result, 'failure') }}
     steps:
-      - uses: mattermost/action-mattermost-notify@master
+      - uses: mattermost/action-mattermost-notify@b7d118e440bf2749cd18a4a8c88e7092e696257a # v2.0.0
         if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
         with:
           MATTERMOST_WEBHOOK_URL: ${{ secrets.MM_WEBHOOK_URL }}

.github/workflows/sync.yml

@@ -55,7 +55,7 @@ jobs:
     if: ${{ needs.sync.outputs.file_size != '0' && needs.sync.outputs.sync_exit_code != '0' }}
     steps:
       - name: Send notify
-        uses: mattermost/action-mattermost-notify@master
+        uses: mattermost/action-mattermost-notify@b7d118e440bf2749cd18a4a8c88e7092e696257a # v2.0.0
         with:
           MATTERMOST_WEBHOOK_URL: ${{ secrets.MM_WEBHOOK_DEV }}
           TEXT: |