[ticket/12823] Remove all trailing whitespace

Almost all of the css files have aspects that contain trailing whitespace in the selector lines.
This is very annoying as any changes I make with my editor it automatically removes it which causes unnecessary changes to unaffected lines
There fore I have re-saved all of the files without editing them to remove all the trailing whitespace

Ticket: https://tracker.phpbb.com/browse/PHPBB3-12823

PHPBB3-12823