Similar to T105570: Remove old user groups from Wikimedia wikis (afttest, afttest-hide, etc.).
These two groups no longer have any rights related to Extension:CodeReview. There're no reason to keep them. Just remove them from $wgAddGroups and $wgRemoveGroups.
Existed members of coder group except admins should be moved to "autoreview" group.
Announcement: https://www.mediawiki.org/wiki/Project:Requests#Delete_.22coder.22_and_.22svnadmins.22_group