repl: fix permanent deoptimizations

PR-URL: https://github.com/nodejs/node/pull/12456
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/repl.js

@@ -601,10 +601,10 @@ REPLServer.prototype.createContext = function() {
     }
   }
 
-  const module = new Module('<repl>');
+  var module = new Module('<repl>');
   module.paths = Module._resolveLookupPaths('<repl>', parentModule, true) || [];
 
-  const require = internalModule.makeRequireFunction(module);
+  var require = internalModule.makeRequireFunction(module);
   context.module = module;
   context.require = require;