Follow best practice, remove closing PHP tag

See http://drupal.org/coding-standards :

Removing it eliminates the possibility for unwanted whitespace at the end of files which can cause "header already sent" errors, XHTML/XML validation issues, and other problems.
The closing delimiter at the end of a file is optional.
PHP.net itself removes the closing delimiter from the end of its files (example: prepend.inc), so this can be seen as a "best practice."