Update CI to use checkout v4

Author: GianniCarlo

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: macos-13
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Create Debug.xcconfig
       run: cp ./BuildConfiguration/Debug.template.xcconfig ./BuildConfiguration/Debug.xcconfig
     - name: Swiftlint