Make it compression=None a valid case

This regression was cased by 78f5542
And missed during review.
compression=None is the same as compression=False, but it is valid now.

Author: dkropachev

cassandra/cluster.py

@@ -685,7 +685,7 @@ class Cluster(object):
     Used for testing new protocol features incrementally before the new version is complete.
     """
 
-    compression: Union[bool, str] = True
+    compression: Union[bool, str, None] = True
     """
     Controls compression for communications between the driver and Cassandra.
     If left as the default of :const:`True`, either lz4 or snappy compression
@@ -1172,7 +1172,7 @@ def token_metadata_enabled(self, enabled):
     def __init__(self,
                  contact_points=_NOT_SET,
                  port=9042,
-                 compression: Union[bool, str] = True,
+                 compression: Union[bool, str, None] = True,
                  auth_provider=None,
                  load_balancing_policy=None,
                  reconnection_policy=None,
@@ -1285,7 +1285,7 @@ def __init__(self,
 
         self._resolve_hostnames()
 
-        if isinstance(compression, bool):
+        if isinstance(compression, bool) or compression is None:
             if compression and not locally_supported_compressions:
                 log.error(
                     "Compression is enabled, but no compression libraries are available. "