Add missing --allow-natives-syntax flag to test case

test/mjsunit/regress/regress-crbug-125148.js

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+// Flags: --allow-natives-syntax
+
 var A = {
   foo: function() { assertUnreachable(); }
 }
 
 var B = {
   b: 2,
   foo: function() { return 1; }
 }
 B.__proto__ = A;
 
 var C = {};
 C.__proto__ = B;
 
 function bar(x) {
   return x.foo();
 }
 
 for (var i = 0; i < 3; i++) {
   assertEquals(1, bar(C));
 }
 %OptimizeObjectForAddingMultipleProperties(B, 100);  // Force dictionary mode.
 %OptimizeFunctionOnNextCall(bar);
 assertEquals(1, bar(C));