Update default port in Manager.connect to use None instead of integer value

This was the default behavior for launch. For a value type, where the
absense of the port doesn't really matter, using `int` instead of
`Optional[int]` makes more sense, but consistency is more important, and
switching launch to `int` could break user code.

Author: huffman

python/saleae/automation/manager.py

@@ -397,7 +397,7 @@ def fail(reason: str):
     def connect(cls,
                 *,
                 address: str = _DEFAULT_GRPC_ADDRESS,
-                port: int = _DEFAULT_GRPC_PORT,
+                port: Optional[int] = None,
                 connect_timeout_seconds: Optional[float] = None,
                 grpc_channel_arguments: Optional[List[Tuple[str, Any]]] = None) -> 'Manager':
         """Connect to an existing instance of Logic 2.
@@ -408,6 +408,9 @@ def connect(cls,
         :param grpc_channel_arguments: See __init__
         """
 
+        if port is None:
+            port = _DEFAULT_GRPC_PORT
+
         return cls(address=address,
                    port=port,
                    connect_timeout_seconds=connect_timeout_seconds,