debugger: remove obsolete setTimeout

Remove obsolete `setTimeout()` introduced in 3148f14. The fix for the
problem is in b266074. (For the record, I mostly don't know what I'm
talking about here but am summarizing from an IRC #node-dev conversation
with @indutny on 04-Jun-2016.)

PR-URL: #7154
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: Trott

lib/_debugger.js

@@ -825,13 +825,7 @@ function Interface(stdin, stdout, args) {
   // Run script automatically
   this.pause();
 
-  // XXX Need to figure out why we need this delay
-  setTimeout(function() {
-
-    self.run(function() {
-      self.resume();
-    });
-  }, 10);
+  setImmediate(() => { this.run(); });
 }