Use GITHUB_OUTPUT file per docs

Author: jasonkarns

.github/workflows/definitions.yml

@@ -23,7 +23,7 @@ jobs:
     - id: log
       run: |
         msg=$(git log --format='- %s' --reverse ${{github.sha}}..)
-        echo "message=${msg//$'\n'/'%0A'}" >> $GITHUB_ENV
+        echo "message=${msg//$'\n'/'%0A'}" >> $GITHUB_OUTPUT
     - uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e # v7.0.8
       with:
         token: ${{ secrets.BOT_TOKEN }}