Remove code for MongoDB < 3.6 support

$ git grep "max_wire_version <" | tee

auth.py:    if credentials.username is None and sock_info.max_wire_version < 5:

auth_aws.py:    if sock_info.max_wire_version < 9:

bulk.py:        if sock_info.max_wire_version < 5:

bulk.py:        if sock_info.max_wire_version < 6 and self.uses_array_filters:

change_stream.py:                            (exc._max_wire_version < 9 and

client_session.py:            if sock_info.max_wire_version < 13:

collection.py:            if sock_info.max_wire_version < 5:

collection.py:            if sock_info.max_wire_version < 6:

collection.py:            if sock_info.max_wire_version < 5:

collection.py:            if sock_info.max_wire_version < 5:

collection.py:            if sock_info.max_wire_version < 5:

collection.py:                if sock_info.max_wire_version < 6:

collection.py:                if sock_info.max_wire_version < 8:

message.py:        if sock_info.max_wire_version < 5 and self.collation is not None:

message.py:        if sock_info.max_wire_version < 4 and self.allow_disk_use is not None:

mongo_client.py:                        sock_info.max_wire_version < 8):

pool.py:        if (read_concern and self.max_wire_version < 4

pool.py:        elif self.max_wire_version < 5 and collation is not None:

topology.py:                if is_shutting_down or (err_ctx.max_wire_version <= 7):

topology_description.py:                and s.max_wire_version < common.MIN_SUPPORTED_WIRE_VERSION)