fluxbox: do not autoreconf

There is no need to have "AUTORECONF = YES" since the patch which
modified the "configure.in" file was removed in the last version bump.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>