Remove more dead code after Object.observe removal

test/mjsunit/regress/regress-1240.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // This regression tests that we are not allowed to overwrite an existing
 // non-configurable getter with a new getter. In addition, we should not
 // be able to change the configurable flag from false to true.
 
 var a = {};
 Object.defineProperty(a, 'b',
                       { get: function () { return 42; }, configurable: false });
 // Do not allow us to redefine b on a.
-a.__defineGetter__('b', function _b(){ return 'foo'; });
+try {
+  a.__defineGetter__('b', function _b(){ return 'foo'; });
+} catch (e) {}
 assertEquals(42, a.b);
 var desc = Object.getOwnPropertyDescriptor(a, 'b');
 assertFalse(desc.configurable);