[NFC] Remove unused member function 'Error' from PCHValidator

As the title suggested.

Author: ChuanqiXu9

clang/include/clang/Serialization/ASTReader.h

@@ -312,9 +312,6 @@ class PCHValidator : public ASTReaderListener {
                                StringRef SpecificModuleCachePath,
                                bool Complain) override;
   void ReadCounter(const serialization::ModuleFile &M, unsigned Value) override;
-
-private:
-  void Error(const char *Msg);
 };
 
 /// ASTReaderListenter implementation to set SuggestedPredefines of

clang/include/clang/Serialization/ASTRecordReader.h

@@ -370,10 +370,6 @@ struct SavedStreamPosition {
   uint64_t Offset;
 };
 
-inline void PCHValidator::Error(const char *Msg) {
-  Reader.Error(Msg);
-}
-
 } // namespace clang
 
 #endif