fix: support ISO 8601 timestamp format in Packet.sniff_time for tshark 4.6+ JSON/EK output

Author: GaoJian

src/pyshark/packet/packet.py

@@ -83,6 +83,8 @@ def __bool__(self):
 
     @property
     def sniff_time(self) -> datetime.datetime:
+        if self.sniff_timestamp[-1] == 'Z':
+            return datetime.datetime.fromisoformat(self.sniff_timestamp)
         try:
             timestamp = float(self.sniff_timestamp)
         except ValueError: