PYTHON-1649 Bump max wire version to 8 (MongoDB 4.2)

Author: ShaneHarvey

pymongo/common.py

@@ -53,7 +53,7 @@
 # What this version of PyMongo supports.
 MIN_SUPPORTED_SERVER_VERSION = "2.6"
 MIN_SUPPORTED_WIRE_VERSION = 2
-MAX_SUPPORTED_WIRE_VERSION = 5
+MAX_SUPPORTED_WIRE_VERSION = 8
 
 # Frequency to call ismaster on servers, in seconds.
 HEARTBEAT_FREQUENCY = 10