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

test/mjsunit/compiler/osr-block-scope-func.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
 
 "use strict";
 
 function foo() {
   var result;
   {
     let sum = 0;
     for (var i = 0; i < 100; i++) {
       if (i == 50) %OptimizeOsr();
       sum += i;
     }
     result = ret;
     function ret() {
       return sum;
     }
   }
   return result;
 }
 
 assertEquals(4950, foo()());
 assertEquals(4950, foo()());
 assertEquals(4950, foo()());