Remove warning comment from FORCE_SYNC

Remove warning comment from FORCE_SYNC

There is a legitimate reason for clients to force a sync on the device.
X.Org drivers lose the fd when the device is disabled and re-enabled. When
the device comes back, a simple libevdev_change_fd() doesn't update the status
on the device.

Button states, etc. may have changed, etc. So a driver may call FORCE_SYNC after
re-connecting to the fd to make sure the library and the driver get the current
state of the device.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>