bug 29922 removes the abusefilter-private user rights from $wgAvailableRights.
But you have to clean up the use of that user rights inside CentralAuth. The user right was assigned to the global group sysadmin while removing. It is shown as set when getting the user rights of a user with the api (see url as example).
Maybe other global groups has this right also set. Please remove it from the sysadmins group and check all other groups. The best way is, to enable the user right, remove it from [[meta:Special:GlobalGroupPermissions/sysadmin]] (which produce a log entry for transparent) and then disable it again.
Another way is to check in CentralAuth against $wgAvailableRights before giving the rights back or do permissions check. If that is better, move this bug to CentralAuth (or create/clone a new bug).