repl: fix deprecation code

This slipped through while landing.

PR-URL: #15668
Refs: #15136
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

lib/repl.js

@@ -694,7 +694,7 @@ REPLServer.prototype.setPrompt = function setPrompt(prompt) {
 REPLServer.prototype.turnOffEditorMode = util.deprecate(
   function() { _turnOffEditorMode(this); },
   'REPLServer.turnOffEditorMode() is deprecated',
-  'DEP00XX');
+  'DEP0078');
 
 // A stream to push an array into a REPL
 // used in REPLServer.complete