Correct misleading verbiage in 'print' hook docs.

Standardizes 'print' hook docs on the concept that hooks are fired when scripts and styles are printed.

Props ericlewis for the initial patch.
Fixes #26924.

Built from https://develop.svn.wordpress.org/trunk@27695


git-svn-id: http://core.svn.wordpress.org/trunk@27534 1a063a9b-81f0-0310-95a4-ce76da25c4cd