Try github.event.release.tag_name

I think GITHUB_REF_NAME isn't defined. GITHUB_REF will be but we'd need
to parse it.

Author: microbit-matt-hillsdon

.github/workflows/release.yml

@@ -26,8 +26,8 @@ jobs:
       - uses: microbit-foundation/[email protected]
         with:
           file: app/build/outputs/bundle/release/app-release.aab
-          asset_name: microbit-release-${{ env.GITHUB_REF_NAME }}.aab
+          asset_name: microbit-release-${{ github.event.release.tag_name }}.aab
       - uses: microbit-foundation/[email protected]
         with:
           file: app/build/outputs/apk/release/app-release.apk
-          asset_name: microbit-release-${{ env.GITHUB_REF_NAME }}.apk
+          asset_name: microbit-release-${{ github.event.release.tag_name }}.apk