Update GetCurrentTime to use datetime.datetime.now

`datetime.datetime.utcnow` is apparently deprecated. The suggested fix is to use timezone-aware objects.

PiperOrigin-RevId: 748738057

Author: protobuf-github-bot

python/google/protobuf/internal/well_known_types.py

@@ -181,7 +181,7 @@ def FromJsonString(self, value):
 
   def GetCurrentTime(self):
     """Get the current UTC into Timestamp."""
-    self.FromDatetime(datetime.datetime.utcnow())
+    self.FromDatetime(datetime.datetime.now(tz=datetime.timezone.utc))
 
   def ToNanoseconds(self):
     """Converts Timestamp to nanoseconds since epoch."""