jquery.suggestions: Remove dead code for returning options

jquery.suggestions: Remove dead code for returning options

    returnValue = (key in obj) ? undefined : obj[key];

By standard, this cannot return anything other undefined.
This code has been broken since the introduction of the module
in 2012 (32377424b, r72349).

The functionality also didn't have test (naturally), and isn't
used anywhere in Wikimedia Git. Simply remove it.

Also remove the confusing $() wrapping of the non-getter return
value that provides chainability.

The 'this' inside a jQuery method is already an instance of jQuery,
pulling it through $() again achieves very little.

Change-Id: Id13861d42b65a759d74670d8c5850aecee4daf7d