clang: fix typo availbility

- Fixes [[ https://github.com/llvm/llvm-project/issues/56787 | #56787 ]].

I am fixing the spelling of availability.

I am unsure if this change will have any side effects. If someone can
help on how to check if it has any side effects, I can test those out as
well.

Reviewed By: inclyc

Differential Revision: https://reviews.llvm.org/D131277

clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp

@@ -494,7 +494,7 @@ SymbolGraphSerializer::serializeAPIRecord(const RecordTy &Record) const {
   serializeObject(
       Obj, "location",
       serializeSourceLocation(Record.Location, /*IncludeFileURI=*/true));
-  serializeObject(Obj, "availbility",
+  serializeObject(Obj, "availability",
                   serializeAvailability(Record.Availability));
   serializeObject(Obj, "docComment", serializeDocComment(Record.Comment));
   serializeArray(Obj, "declarationFragments",