timers: remove unreachable code

Author: yorkie

lib/timers.js

@@ -333,7 +333,6 @@ exports.setTimeout = function(callback, after) {
   var ontimeout = callback;
   switch (length) {
     // fast cases
-    case 0:
     case 1:
     case 2:
       break;
@@ -392,7 +391,6 @@ exports.setInterval = function(callback, repeat) {
   var length = arguments.length;
   var ontimeout = callback;
   switch (length) {
-    case 0:
     case 1:
     case 2:
       break;
@@ -605,7 +603,6 @@ exports.setImmediate = function(callback, arg1, arg2, arg3) {
 
   switch (arguments.length) {
     // fast cases
-    case 0:
     case 1:
       break;
     case 2: