Update unity-package.yml

Author: ricardj

.github/workflows/unity-package.yml

@@ -39,6 +39,6 @@ jobs:
         with:
           artifacts: "ModelInstanceCollection.unitypackage"
           name: "ModelInstanceCollection"
-          tag: $release_tag
+          tag: ${{env.release_tag}}
           #tag: v1
           github_token: ${{ secrets.GITHUB_TOKEN }}