ci: Refactor Github Action per b/485167538 (gemini-cli-extensions#99)

Co-authored-by: Ben Knutson <benknutson@google.com>
Co-authored-by: Averi Kitsch <akitsch@google.com>

Author: 3 people

.github/workflows/package-and-upload-assets.yml

@@ -132,7 +132,8 @@ jobs:
       - name: Upload all assets to GitHub Release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_EVENT_RELEASE_TAG_NAME: ${{ github.event.release.tag_name }}
         run: |
           gh release upload \
-            ${{ github.event.release.tag_name }} \
+            ${GITHUB_EVENT_RELEASE_TAG_NAME} \
             release-archives/*/*