Replace a redundant ! is_preview() check with a more appropriate one.

fixes #20496.
Built from https://develop.svn.wordpress.org/trunk@28928


git-svn-id: http://core.svn.wordpress.org/trunk@28726 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove obsolete comment in `wptexturize()`.

http://irclogs.wordpress.org/chanlog.php?channel=wordpress-dev&day=2014-06-30&sort=asc#m879104

See [28831].

Built from https://develop.svn.wordpress.org/trunk@28929


git-svn-id: http://core.svn.wordpress.org/trunk@28727 1a063a9b-81f0-0310-95a4-ce76da25c4cd