Update cms branch references to correct versions

Context: https://gitlab.com/adblockinc/websites-team/adblockplus-org/-/issues/31

Once cms!17 (merged) is merged, the master branch of the cms referenced in the eyeo-python2.7-cms dockerfile will no longer be correct.

Similarly the migration-to-python3 cms branch referenced in the adblockinc-cms-202208.1 dockerfile may no longer be available is it would've been merged into master.