Use v4

Author: BerendWouters

.github/workflows/master_weu-spaceapi-linux.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Set up .NET Core
         uses: actions/setup-dotnet@v1