Remove logical partitions from ab_partitions.txt in retrofit package.

For retrofit updates:
ab_partitions -= dynamic_partition_list
ab_partitions += super_block_devices

For example,
if super_block_devices == ["system", "vendor", "odm"] and
   dynamic_partition_list == ["system", "vendor", "product"],
product partition needs to be removed from ab_partitions.txt
otherwise brillo_update_payload will generate a payload with
product partition in it.

Test: retrofit update that adds a partition
Fixes: 127425410

Change-Id: Id79a410cee3c611ac50d27f14282916aea34f938