Update unit-test.yml

fix ubuntu version

Author: BerndSchuller

.github/workflows/unit-test.yml

@@ -10,7 +10,7 @@ on:
 jobs:
   unit-test:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
         python-version: ["3.7", "3.x"]