Avoid use of deprecated GH actions features

Author: thomaseizinger

.github/workflows/publish-new-release.yml

@@ -19,15 +19,15 @@ jobs:
           BRANCH_NAME="${{ github.event.pull_request.head.ref }}"
           VERSION=${BRANCH_NAME#release/}
 
-          echo "::set-env name=RELEASE_VERSION::$VERSION"
+          echo "RELEASE_VERSION=$VERSION" >> $GITHUB_ENV
 
       - name: Extract version from branch name (for hotfix branches)
         if: startsWith(github.event.pull_request.head.ref, 'hotfix/')
         run: |
           BRANCH_NAME="${{ github.event.pull_request.head.ref }}"
           VERSION=${BRANCH_NAME#hotfix/}
 
-          echo "::set-env name=RELEASE_VERSION::$VERSION"
+          echo "RELEASE_VERSION=$VERSION" >> $GITHUB_ENV
 
       - name: Create Release
         uses: thomaseizinger/create-release@1.0.0