ci(workflows): migrate to GITHUB_OUTPUT in release-helm workflow

Update release-helm workflow to use the modern $GITHUB_OUTPUT file
format instead of the deprecated ::set-output command for setting
workflow outputs in GitHub Actions.

Co-Authored-By: Claude <[email protected]>

Author: STRRL

.github/workflows/release-helm.yaml

@@ -17,7 +17,7 @@ jobs:
         run: |
           GIT_TAG=${GITHUB_REF##*/}
           VERSION=${GIT_TAG##v}
-          echo "::set-output name=version::$(echo $VERSION)"
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
       - name: Publish Helm chart
         uses: stefanprodan/helm-gh-pages@master
         with: