[ci] Release from ref instead of branch name (HaxeFoundation#1328)

The branch may have been updated since the ci started, so we need to use
the full ref instead of the branch name.

Author: tobil4sk

.github/workflows/package.yml

@@ -135,8 +135,8 @@ jobs:
           uses: ncipollo/release-action@v1
           with:
             tag: v${{ env.hxcpp_release }}
-            commit: ${{ github.head_ref }}
+            commit: ${{ github.ref }}
             name: Release ${{ env.hxcpp_release }}
             draft: false
             prerelease: false
-            artifacts: ./hxcpp-${{ env.hxcpp_release }}.zip
+            artifacts: ./hxcpp-${{ env.hxcpp_release }}.zip