Remove serverless feature

Drop ScyllaCloud/serverless feature, it was dropped from cloud and not
comming back.

Author: dkropachev

cassandra/cluster.py

@@ -95,7 +95,6 @@
                                       GraphSON3Serializer)
 from cassandra.datastax.graph.query import _request_timeout_key, _GraphSONContextRowFactory
 from cassandra.datastax import cloud as dscloud
-from cassandra.scylla.cloud import CloudConfiguration
 from cassandra.application_info import ApplicationInfoBase
 
 try:
@@ -1238,23 +1237,7 @@ def __init__(self,
             self.connection_class = connection_class
 
         if scylla_cloud is not None:
-            if contact_points is not _NOT_SET or ssl_context or ssl_options:
-                raise ValueError("contact_points, ssl_context, and ssl_options "
-                                 "cannot be specified with a scylla cloud configuration")
-            if shard_aware_options and not shard_aware_options.disable_shardaware_port:
-                raise ValueError("shard_aware_options.disable_shardaware_port=False "
-                                 "cannot be specified with a scylla cloud configuration")
-            uses_twisted = TwistedConnection and issubclass(self.connection_class, TwistedConnection)
-            uses_eventlet = EventletConnection and issubclass(self.connection_class, EventletConnection)
-
-            scylla_cloud_config = CloudConfiguration.create(scylla_cloud, pyopenssl=uses_twisted or uses_eventlet,
-                                                            endpoint_factory=endpoint_factory)
-            ssl_context = scylla_cloud_config.ssl_context
-            endpoint_factory = scylla_cloud_config.endpoint_factory
-            contact_points = scylla_cloud_config.contact_points
-            ssl_options = scylla_cloud_config.ssl_options
-            auth_provider = scylla_cloud_config.auth_provider
-            shard_aware_options = ShardAwareOptions(shard_aware_options, disable_shardaware_port=True)
+            raise NotImplementedError("scylla_cloud was removed and not supported anymore")
 
         if cloud is not None:
             self.cloud = cloud