ubuntu-20.04 instead, test for now

Author: asg017

.github/workflows/test.yaml

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