[ast] Remove unused function Scope::ReportMessage.

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index 088710b8dde0eec7ae821f5d707c9689c6724099..cb1fb5bdac5659f2aa71ffd4bb074e227e3546fa 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -571,11 +571,6 @@ class Scope: public ZoneObject {
     return &sloppy_block_function_map_;
   }
 
-  // Error handling.
-  void ReportMessage(int start_position, int end_position,
-                     MessageTemplate::Template message,
-                     const AstRawString* arg);
-
   // ---------------------------------------------------------------------------
   // Debugging.