Remove redundant WP_JSON_Pages::type_archive_link()

The `WP_JSON_Pages::type_archive_link()` function is identical to the [`WP_JSON_CustomPostType::type_archive_link()` function](https://github.com/WP-API/WP-API/blob/f3ea834f857adf1fd6089ba2b4ccda94c36cbb7a/lib/class-wp-json-customposttype.php#L207:L214), so it can be removed.