C#: Disregard destructors in model generation.

csharp/ql/src/utils/model-generator/internal/CaptureModelsSpecific.qll

@@ -36,7 +36,8 @@ private predicate isRelevantForModels(CS::Callable api) {
   api.getDeclaringType().getNamespace().getQualifiedName() != "" and
   not api instanceof CS::ConversionOperator and
   not api instanceof Util::MainMethod and
-  not isHigherOrder(api)
+  not isHigherOrder(api) and
+  not api instanceof CS::Destructor
 }
 
 /**

csharp/ql/test/utils/model-generator/Summaries.cs

@@ -6,6 +6,9 @@ namespace Summaries;
 
 public class BasicFlow
 {
+    // No flow summary and no negative summary either.
+    ~BasicFlow() { }
+
     private string tainted;
 
     public BasicFlow ReturnThis(object input)