Delete sstable_streamed_mutation
Delete sstable_streamed_mutation

It's no longer used so can be safely removed.

Signed-off-by: Piotr Jastrzebski <2c0eb4a25a7cde333ff2d0860cb06051925fd74f@scylladb.com>

scylladb/scylla,duarten/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla