ci: Switch from Mac to Ubuntu

Author: jmgate

.github/workflows/continuous-integration.yml

@@ -13,7 +13,7 @@ defaults:
 
 jobs:
   test:
-    runs-on: macos-latest
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         version: ["3.8", "3.9", "3.10", "3.11", "3.12"]