Remove json2 JS script and the try except around seal

 * Remove json2 all supported runtimes have the JSON now

 * Remove the try except for broken seal in 1.9.x we don't support 1.9.x and it
   worked in 1.8.x and then in 60+ (at least, we don't support anything lower).

1.8.5
```
% js --help 2>&1 | grep 185
  185:  JavaScript 1.8.5 (default)
% js
js>  var a=[1,2,3]; Object.freeze(a); a[1]=100; a
[1, 2, 3]
```

78
```
% js78
var a=[1,2,3]; Object.freeze(a); a[1]=100; a
[1, 2, 3]
js>
```

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=449657#c0