Replace release-branches.py with TS version in release-branches action

Author: mbg

.github/actions/release-branches/action.yml

@@ -22,7 +22,8 @@ runs:
         MAJOR_VERSION: ${{ inputs.major_version }}
         LATEST_TAG: ${{ inputs.latest_tag }}
       run: |
-        python ${{ github.action_path }}/release-branches.py \
+        npm ci
+        npx tsx ./pr-checks/release-branches.ts \
             --major-version "$MAJOR_VERSION" \
             --latest-tag "$LATEST_TAG"
       shell: bash