feeds.conf.default: enable video feed by default

feeds.conf.default: enable video feed by default

As discussed in the previous OpenWrt meeting the easiest way to have
regular builds of packages on the video feed without adding additional
complexity is by enabling the video feed by default.
If that slows down the buildbots beyond being useful we can always
disable it again and find another way to only sporadically build
packages of the video feed.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>