fix: update OSPO action references to canonical org path

The OSPO actions have moved from github/ to github-community-projects/.
Update workflow references to use the canonical org path.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: zkoppert

.github/workflows/issue-metrics.yml

@@ -29,7 +29,7 @@ jobs:
         echo "last_month=$first_day..$last_day" >> "$GITHUB_ENV"
 
     - name: Run issue-metrics tool
-      uses: github/issue-metrics@v3
+      uses: github-community-projects/issue-metrics@v3
       env:
         GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         SEARCH_QUERY: 'repo:zarr-developers/zarr-python is:issue created:${{ env.last_month }} -reason:"not planned"'