scylla-artifacts.py: Adjust io queue params
scylla-artifacts.py: Adjust io queue params

The very conservative settings our testing uses is now
causing problems with the io queue params sanity check:

Reason found: I/O Queue capacity for this shard is too low (1, minimum 4 expected)

So let's bump the params a little so we don't have this
problem.

Signed-off-by: Lucas Meneghel Rodrigues <8ad3460456640ab580599f5440c5a8d925a620b9@scylladb.com>

scylladb/scylla-artifact-tests,lmr/scylla-artifact-tests,scylladb/scylla-artifact-tests