Update checkout action.

Author: Nihlus

.github/workflows/dotnet.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3
         with:
           dotnet-version: |