ci: Update artifact actions

Author: mycroes-nl

.github/workflows/dotnet.yml

@@ -54,7 +54,7 @@ jobs:
         /p:PackageVersion=${{ steps.gitversion.outputs.semVer }}
         --output ${{ env.NuGetDirectory }}
 
-    - uses: actions/upload-artifact@v3
+    - uses: actions/upload-artifact@v4
       with:
         name: nuget
         if-no-files-found: error
@@ -117,7 +117,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [ create_nuget, run_test ]
     steps:
-      - uses: actions/download-artifact@v3
+      - uses: actions/download-artifact@v4
         with:
           name: nuget
           path: ${{ env.NuGetDirectory }}