[turbofan] Remove deprecated --turbo-osr flag.

test/mjsunit/compiler/osr-forof.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --use-osr --turbo-osr
+// Flags: --use-osr
 
 function f(a) {
   var sum = 0;
   for (var i of a) {
     var x = i + 2;
     var y = x + 5;
     var z = y + 3;
     sum += z;
   }
   return sum;
@@ skipping 10 matching lines @@
 
 function wrap(array) {
   var iterable = {};
   var i = 0;
   function next() {
     return { done: i >= array.length, value: array[i++] };
   };
   iterable[Symbol.iterator] = function() { return { next:next }; };
   return iterable;
 }