Remove debug code from WP_Automatic_Updater::send_email().

Merges [25891] to the 3.7 branch.

props markmcwilliams for initial patch.
fixes #25678.


git-svn-id: https://develop.svn.wordpress.org/branches/3.7@25892 602fd350-edb4-49c9-b593-d223f7449a82