misc: Unused migration admin removed

Co-authored-by: Victor Naumik <vicnaum@gmail.com>

contracts/libraries/constants/Types.sol

@@ -411,6 +411,5 @@ library Types {
         address legacyFeeFollowModule;
         address legacyProfileFollowModule;
         address newFeeFollowModule;
-        address migrationAdmin;
     }
 }