Ensure mjsunit tests use dashes not underscores in flags directives.

test/mjsunit/regress/regress-115452.js

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // Test that a function declaration cannot overwrite a read-only property.
 
-// Flags: --es52_globals
+// Flags: --es52-globals
 
 function foobl() {}
 assertTrue(typeof this.foobl == "function");
 assertTrue(Object.getOwnPropertyDescriptor(this, "foobl").writable);
 
 Object.defineProperty(this, "foobl", {value: 1, writable: false});
 assertSame(1, this.foobl);
 assertFalse(Object.getOwnPropertyDescriptor(this, "foobl").writable);
 
 // This has to run in global scope, so cannot use assertThrows...
 try {
   eval("function foobl() {}");  // Should throw.
   assertUnreachable();
 } catch (e) {
   assertInstanceof(e, TypeError);
 }
 assertSame(1, this.foobl);