Refactor GitHub Actions workflow for pull requests

Updated the GitHub Actions workflow to use 'pull_request' instead of 'pull_request_target' and simplified the checkout steps.

Author: herbertroth

.github/workflows/codeception.yml

@@ -9,7 +9,7 @@ on:
             - "[0-9]+.[0-9]+"
             - "[0-9]+.x"
             - "feature-*"
-    pull_request_target:
+    pull_request:
         types: [opened, synchronize, reopened]
 
 env:
@@ -24,17 +24,8 @@ jobs:
             matrix: ${{ steps.set-matrix.outputs.matrix }}
             private_repo: ${{ env.PRIVATE_REPO }}
         steps:
-            - name: Checkout PR head (only for pull_request_target)
-              if: github.event_name == 'pull_request_target'
-              uses: "actions/checkout@v4"
-              with:
-                ref: "refs/pull/${{ github.event.pull_request.number }}/merge"
-
-            - name: Checkout PR head (for push or other events)
-              if: github.event_name != 'pull_request_target'
-              uses: "actions/checkout@v4"
-              with:
-                  ref: ${{ github.ref }}
+            - name: Checkout code
+              uses: actions/checkout@v4
 
             - name: Checkout reusable workflow repo
               uses: actions/checkout@v4