C#: Address review comments.

csharp/ql/test/library-tests/dataflow/library/FlowSummariesFiltered.ql

@@ -13,7 +13,7 @@ class IncludeFilteredSummarizedCallable extends IncludeSummarizedCallable {
     this.propagatesFlow(input, output, preservesValue) and
     not exists(IncludeSummarizedCallable rsc |
       isBaseCallableOrPrototype(rsc) and
-      rsc.(SummarizedCallableImpl).propagatesFlow(input, output, preservesValue) and
+      rsc.propagatesFlow(input, output, preservesValue) and
       this.(UnboundCallable).overridesOrImplementsUnbound(rsc)
     )
   }

csharp/ql/test/shared/FlowSummaries.qll

@@ -17,6 +17,4 @@ class IncludeSummarizedCallable extends SummarizedCallableImplFinal {
   ) {
     this.propagatesFlow(input, output, preservesValue)
   }
-
-  string toString() { result = super.toString() }
 }