Start analysing merge commit for PRs

.github/workflows/codeql.yml

@@ -14,16 +14,6 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-      with:
-        # Must fetch at least the immediate parents so that if this is
-        # a pull request then we can checkout the head of the pull request.
-        fetch-depth: 2
-
-    # If this run was triggered by a pull request event then checkout
-    # the head of the pull request instead of the merge commit.
-    - run: git checkout HEAD^2
-      if: ${{ github.event_name == 'pull_request' }}
-
     - uses: ./init
       with:
         languages: javascript