jQuery.boxModel should be listed as removed

[`jQuery.boxModel`](http://api.jquery.com/jQuery.boxModel/) was [removed in 1.8](/jquery/jquery/commit/c4e22ad8b5edd52ac78ec44bf7df8a7f37403623#diff-6d4bb79610683d9749d2cbb62e708d88). There should probably be a note in the doc to this effect, similar to what's in the doc for `jQuery.browser`:

> This property was removed in jQuery [1.8] and is available only through the jQuery.migrate plugin. Please try to use feature detection instead.

Possibly also add this to the "[Removed](http://api.jquery.com/category/removed/)" category?

`jQuery.support.boxModel` was also [removed in 1.10](/jquery/jquery/pull/1231), so perhaps the reference to `jQuery.support` should also be removed from the `boxModel` doc.