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

test/mjsunit/compiler/osr-backedges1.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: --allow-natives-syntax --use-osr --turbo-osr
+// Flags: --allow-natives-syntax --use-osr
 
 function foo(a) {
   var i = a | 0;
   while (true) {
     if (i == 0) { i = 1; continue; }
     if (i == 1) { i = 2; continue; }
     if (i == 2) { i = 3; continue; }
     if (i == 3) { i = 4; continue; }
     if (i == 4) { i = 5; continue; }
     if (i == 5) { i = 6; continue; }
     if (i == 6) { i = 7; continue; }
     if (i == 7) { i = 8; continue; }
     for (var j = 0; j < 10; j++) { if (i == 5) %OptimizeOsr(); }
     break;
   }
   return j;
 }
 
 function test(func, tv, fv) {
   assertEquals(tv, func(0));
   assertEquals(tv, func(0));
   assertEquals(fv, func(9));
   assertEquals(fv, func(9));
 }
 
 test(foo, 10, 10);