Fixes for hooks documentation in wp-admin/admin-footer.php.

Adds some new lines, some hook-line spacing, docs-specific variables, and other language tweaks.

See #26869, #25229, [25252].

Built from https://develop.svn.wordpress.org/trunk@27145


git-svn-id: https://core.svn.wordpress.org/trunk@27012 1a063a9b-81f0-0310-95a4-ce76da25c4cd