Delete test_freezing_streamed_mutations
Delete test_freezing_streamed_mutations

It tests freeze(streamed_mutation) which is no longer used
and will be removed in the next patch.

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

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