Java: Remove low-confidence dispatch to known neutrals.

java/ql/lib/semmle/code/java/dispatch/ObjFlow.qll

@@ -236,6 +236,8 @@ private VirtualMethodAccess objectToString(ObjNode n) {
   result.getQualifier() = n.asExpr() and sink(n)
 }
 
+predicate objectToStringCall(VirtualMethodAccess ma) { ma = objectToString(_) }
+
 /**
  * Holds if the qualifier of the `Object.toString()` call `ma` might have type `t`.
  */

java/ql/lib/semmle/code/java/dispatch/VirtualDispatch.qll

@@ -93,7 +93,8 @@ private module Dispatch {
       exists(RefType t | qualUnionType(ma, t, false) |
         lowConfidenceDispatchType(t.getSourceDeclaration())
       )
-    )
+    ) and
+    not ObjFlow::objectToStringCall(ma)
   }
 
   private predicate lowConfidenceDispatchType(SrcRefType t) {