Simplify a conditional in order to avoid a warning under MSVC

We were using some convoluted logic here to check if the result of a
`bool` returning function was false, causing MSVC to give a warning
about "'>': unsafe use of type 'bool' in operation". This just removes
the greater-than comparison of the bool against zero.

clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp

@@ -839,7 +839,7 @@ void SymbolGraphSerializer::visitObjCCategoryRecord(
     return;
 
   // Check if the current Category' parent has been visited before, if so skip.
-  if (!(visitedCategories.contains(Record.Interface.Name) > 0)) {
+  if (!visitedCategories.contains(Record.Interface.Name)) {
     visitedCategories.insert(Record.Interface.Name);
     Object Obj;
     serializeObject(Obj, "identifier",