ci(system-tests): run on pull requests

Author: florentinl

.github/workflows/build_layer.yml

@@ -38,7 +38,7 @@ jobs:
       fail-fast: false
       matrix:
         arch: [arm64, amd64]
-        python_version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python_version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
 
     steps:
       - name: Checkout