Reduce the number of test runs in CI.

See https://adamj.eu/tech/2025/05/14/github-actions-avoid-simple-on/

Author: tim-schilling

.github/workflows/test.yml

@@ -2,6 +2,10 @@ name: Test
 
 on:
   push:
+    branches:
+    - main
+    tags:
+    - '**'
   pull_request:
   schedule:
     # Run weekly on Saturday