Remove obsolete `wp_cache_delete('get_pages', 'posts')` from `clean_post_cache()`.

Fixes #27459.

Built from https://develop.svn.wordpress.org/trunk@28875


git-svn-id: http://core.svn.wordpress.org/trunk@28674 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Make the posts list table mode a sticky user setting. props garyc40, azaozz, ericmann. fixes #16774, #20335.

Built from https://develop.svn.wordpress.org/trunk@28876


git-svn-id: http://core.svn.wordpress.org/trunk@28675 1a063a9b-81f0-0310-95a4-ce76da25c4cd