Support branches, so pmbootstrap won't fail if v20.05 is selected:
ERROR: You have an outdated version of the 'apk' package manager installed
(your version: 2.10.5-r1, expected at least: 2.12.1-r0).
Move the logic for this check to pmb.helpers.apk.check_outdated and
adjust the test.
This fixes the CI failure in test_crossdirect_rust, which uses the
stable channel. (My bad for not creating this patch earlier, while at
the same time explaining in the creating pmbootstrap release instructions,
that this minimum apk version should be adjusted.)
69cd7895e2