GHA: Use current checkout

...

Author: helje5

.github/workflows/swift.yml

@@ -15,7 +15,7 @@ jobs:
         with:
           xcode-version: latest
       - name: Checkout Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Build Swift Debug Package
         run: swift build -c debug
       - name: Build Swift Release Package