fix: simplify checkout behavior after changing trigger

Signed-off-by: Fabian Burth <fabian.burth@sap.com>

Author: fabianburth

.github/workflows/codeql.yaml

@@ -9,12 +9,6 @@ on:
     # Run weekly on Monday at 07:25 UTC
     - cron: "25 7 * * 1"
 
-# For pull_request_target events, check out the fork's code.
-# Falls back to the current repository/ref for push and schedule events.
-env:
-  REF: ${{ github.event_name == 'pull_request_target' && github.event.pull_request.head.ref || github.ref }}
-  REPO: ${{ github.event_name == 'pull_request_target' && github.event.pull_request.head.repo.full_name || github.repository }}
-
 # Top-level permissions: restrict to read-only by default.
 permissions:
   contents: read
@@ -46,9 +40,6 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
-        with:
-          repository: ${{ env.REPO }}
-          ref: ${{ env.REF }}
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@45580472a5bb82c4681c4ac726cfdb60060c2ee1 # v3