ci: remove options no longer needed (#540)

.github/workflows/codeql.yml

@@ -11,11 +11,6 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
       - uses: actions/checkout@v2
-        with:
-          fetch-depth: 2
-
-      - run: git checkout HEAD^2
-        if: ${{ github.event_name == 'pull_request' }}
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v1