8254559: Remove unimplemented JVMFlag::get_locked_message_ext

Reviewed-by: dholmes, tschatzl

Author: shipilev

src/hotspot/share/runtime/flags/jvmFlag.hpp

@@ -263,7 +263,6 @@ class JVMFlag {
   void set_product();
 
   JVMFlag::MsgType get_locked_message(char*, int) const;
-  JVMFlag::MsgType get_locked_message_ext(char*, int) const;
 
   static bool is_default(JVMFlagsEnum flag);
   static bool is_ergo(JVMFlagsEnum flag);