C#: Use stubs in the CWE-117 LogForging test.

Author: michaelnebel

csharp/ql/test/query-tests/Security Features/CWE-117/options

@@ -1 +1,3 @@
-semmle-extractor-options: ${testdir}/../../../resources/stubs/System.Web.cs /r:System.Collections.Specialized.dll /r:System.Runtime.Extensions.dll /r:System.Diagnostics.TraceSource.dll
+semmle-extractor-options: /nostdlib /noconfig
+semmle-extractor-options: --load-sources-from-project:${testdir}/../../../resources/stubs/_frameworks/Microsoft.NETCore.App/Microsoft.NETCore.App.csproj
+semmle-extractor-options: ${testdir}/../../../resources/stubs/System.Web.cs