chore(build): retrieve go version from go.mod as single point of truth

.github/workflows/ci.yml

@@ -19,8 +19,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        # renovate: datasource=golang-version depName=golang
-        go-version: 1.23.4
+        go-version-file: go.mod
       id: go
 
     - name: Get dependencies

.github/workflows/codeql.yml

@@ -33,15 +33,6 @@ jobs:
     steps:
     - name: Checkout repository
       uses: actions/checkout@v4
-      with:
-        # We must fetch at least the immediate parents so that if this is
-        # a pull request then we can checkout the head.
-        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' }}
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL