CompactionTask#runMayThrow should not release new SSTables for offline transactions

Right now, CompactionTask#runMayThrow releases new SSTables for offline transactions (code). This change was added in CASSANDRA-8962, prior to the introduction of lifecycle transactions in CASSANDRA-8568. I suspect that this behavior might be undesired and could have just fallen through the cracks.

To my knowledge, this code does not cause any known bugs solely because in-tree tools do not access the SSTables they produce before exiting. However, if someone is to write, say, offline compaction daemon, it might break on subsequent compactions because newly created SSTables will be released.