scylla_lib: drop support for m3 and c3 AWS instance types
scylla_lib: drop support for m3 and c3 AWS instance types

m3 has 80GB SSDs in its largest form and I doubt anybody has ever
used it with Scylla.

I am also not aware of any c3 deployments. Since it is past generation,
it doesn't even show up in the default instance selector anymore.

I propose we drop AMI support for it. In practice, what that means is
that we won't auto-tune its I/O properties and people that want to use
it will have to run scylla_io_setup - like they do today with the EBS
instances.

Signed-off-by: Glauber Costa <7ba9037b0dd006f9408bd45b94707becd5cd4e87@scylladb.com>

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