forgot ubuntu-20.04 for release script...

Author: asg017

.github/workflows/release.yaml

@@ -7,8 +7,8 @@ permissions:
   contents: read
 jobs:
   build-ubuntu:
-    name: Build ubuntu-latest
-    runs-on: ubuntu-latest
+    name: Build ubuntu-20.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - uses: actions/cache@v3