gha: update actions/checkout@v4

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

.github/workflows/ci.yaml

@@ -16,6 +16,6 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: test
       run: make test