[APINotes] Remove unused API

This method is not actually used anywhere.

(cherry picked from commit 4348f32)

Author: egorzhdan

clang/include/clang/APINotes/Types.h

@@ -263,13 +263,6 @@ class ContextInfo : public CommonTypeInfo {
     SwiftObjCMembers = Value.value_or(false);
   }
 
-  /// Strip off any information within the class information structure that is
-  /// module-local, such as 'audited' flags.
-  void stripModuleLocalInfo() {
-    HasDefaultNullability = false;
-    DefaultNullability = 0;
-  }
-
   friend bool operator==(const ContextInfo &, const ContextInfo &);
 
   ContextInfo &operator|=(const ContextInfo &RHS) {