v2022: lava: amd64-upsquared6000: Use weekly image on v2022 1st stage

Follow up from: !483 (merged)

Commit fddc555 ("lava: amd64-upsquared6000: Use v2022 1st stage image
with firmware pkgs") set the UP Squared 6000 1st stage image to a daily
build as it included the required firmware pkgs. As the daily image will
get deleted soon, let's use a weekly one until the next v2022 release it
out.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>