Eliminate use of `extract()` in `post_tags_meta_box()` and `post_categories_meta_box()`.

Both functions only need to read `taxonomy`, yet they extract every available variable from `$box['args']`. Even if those variables were useful, there is no attempt to pass them to anything, and scope in PHP does not allow them to be scooped up by inner functions without being passed directly.
	
See #22400.

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