manual: don't use a comment at the end of the version variable assignment

The comment at the end of the version string assigment could lead to a download
failure so don't use it as a example.

Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Reported-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>