www: url_handlers: Use sizeof() in snprintf
www: url_handlers: Use sizeof() in snprintf

In clear_old_sessions() use sizeof(item) as the size parameter to
snprintf rather than '3'. This should help avoid problems if the size
of item should change.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@opentechlabs.co.uk>

ac000/receiptomatic