Remove redundant assignment. see [28379], [28534].

see #22400.
Built from https://develop.svn.wordpress.org/trunk@28538


git-svn-id: http://core.svn.wordpress.org/trunk@28364 1a063a9b-81f0-0310-95a4-ce76da25c4cd
These functions import `$wpdb` but do not use it.

See #27882.

Built from https://develop.svn.wordpress.org/trunk@28539


git-svn-id: http://core.svn.wordpress.org/trunk@28365 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use correct variable. see [28534], [28538].

see #22400.
Built from https://develop.svn.wordpress.org/trunk@28540


git-svn-id: http://core.svn.wordpress.org/trunk@28366 1a063a9b-81f0-0310-95a4-ce76da25c4cd