Only publish release for tags on this repo

Author: duckontheweb

.github/workflows/release.yml

@@ -9,6 +9,7 @@ jobs:
   release:
     name: release
     runs-on: ubuntu-latest
+    if: ${{ env.GITHUB_REPOSITORY }} == 'stac-utils/pystac'
     steps:
       - uses: actions/checkout@v2