update test workflow to actions/checkout@v4

Author: DannyBen

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Install OS dependencies
       run: sudo apt-get -y install mandoc