mediawiki.api: Remove deprecated function parameters

mediawiki.api: Remove deprecated function parameters

* 'ok' and 'err' parameters to various functions.
  Tracked with mw.track( 'mw.deprecate' ) as 'api.cbParam'.
  Deprecated since MW 1.20, printing console warnings since MW 1.23.
* 'async' parameter to mediawiki.api.category #getCategories.
  Tracked with mw.track( 'mw.deprecate' ) as 'api.async'.
  Deprecated and printing console warnings since MW 1.23.

Also removed is mw.Api#normalizeAjaxOptions, which is no longer needed
and which has never been used by anything outside mediawiki.api module.

Announced in https://www.mail-archive.com/wikitech-l%40lists.wikimedia.org/msg78108.html

Change-Id: I0a650fdb4affd394ae419e21d54baf790116f6f7