reintroduce trigger for PRs only

Author: giohappy

.github/workflows/tests.yml

@@ -1,6 +1,8 @@
 name: GeoNode Test Suites
 
-on: [push, workflow_dispatch]
+on: 
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
 
 jobs:
   # -------------------------------------------------
@@ -9,6 +11,7 @@ jobs:
   build_images:
     name: Build and export Docker images
     runs-on: ubuntu-24.04
+    if: ${{ !github.event.pull_request.draft }}
 
     steps:
       - name: Checkout repository