リリースZIPの作成に使うUbuntuのバージョンを最新版に変更

Author: SofPyon

.github/workflows/release.yml

@@ -9,7 +9,7 @@ name: Upload Release Asset
 jobs:
   build:
     name: Upload Release Asset
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout code
         uses: actions/checkout@v2