Update vulnerability check in dotnet-core workflow

Replaced vulnerable NuGet packages check with a custom command to list vulnerable packages and log the output.

Author: vb2ae

.github/workflows/dotnet-core.yml

@@ -36,8 +36,11 @@ jobs:
       run: dotnet tool install -g nbgv
     - name: Set Version
       run: nbgv cloud  
-    - name: Check vulnerable NuGet packages
-      uses: elmahio/github-check-vulnerable-nuget-packages-action@v2
+    - name: Checking for external vulnerabilites
+      run: |
+        dotnet list package --vulnerable --include-transitive 2>&1 | tee vuln.log
+        echo "Analyze dotnet list package..."
+        ! grep -q -i "has the following vulnerable packages" vuln.log
     - name: Build
       run: dotnet build --configuration Release --no-restore