Eliminate use of `extract()` in `WP_Terms_List_Table::display_rows_or_placeholder()`:

* Set variables for `$page` and `$number`
* `list(...) = $this->get_column_info()` can be removed, as none of the variables returned are used.
* `orderby` and `search` can be checked from `$args`, leaving no reason to extract		

See #22400.

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git-svn-id: http://core.svn.wordpress.org/trunk@28218 1a063a9b-81f0-0310-95a4-ce76da25c4cd