support/script/scancpan: remove duplicated dependency

Dependencies from metacpan comes as a list of modules which is
transformed in a list of distribution for BR.  Different modules could
be included in the same distribution, so duplication is possible.

This can for example be seen with the HTTP-Daemon module, which would
get two times the dependencies on HTTP-Message without this commit.

[Thomas: slightly extend commit log.]

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
user guest
Try-Tiny: add host
Plack: all packages
moo: all packages
dancer2: all packages

TT: PERL_TEMPLATE_TOOLKIT_CONF_OPT = "TT_XS_ENABLE=n"
network interface eth0
defconfig
demo

set BR2_ROOTFS_OVERLAY with $(BR2_EXTERNAL)/overlay/
dancer2 skeleton

$ dancer2 gen -a MyWeb::App
Dancer2 as service
BR demo
add Chart-Plot-Tagged
add ntp in defconfig
update plot