Update to use new $GITHUB_OUTPUT instead of set-output (deephaven#808)

- `set-output` is deprecated: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

.github/workflows/publish-nightly.yml

@@ -20,7 +20,7 @@ jobs:
         continue-on-error: true
         name: check latest commit is less than a day
         if: ${{ github.event_name == 'schedule' }}
-        run: test -z $(git rev-list  --after="24 hours"  ${{ github.sha }}) && echo "::set-output name=should_run::false"
+        run: test -z $(git rev-list  --after="24 hours"  ${{ github.sha }}) && echo "should_run=false" >> $GITHUB_OUTPUT
   publish-nightly:
     needs: check_date
     if: ${{ needs.check_date.outputs.should_run != 'false' }}