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.


git-svn-id: https://develop.svn.wordpress.org/trunk@28390 602fd350-edb4-49c9-b593-d223f7449a82