Fix: Remove datetime field from message response as on the current implementation it is not exported.

Author: nesitor

src/aleph/schemas/api/messages.py

@@ -42,8 +42,10 @@ class MessageConfirmation(BaseModel):
     chain: Chain
     height: int
     hash: str
-    datetime: dt.datetime
 
+    # Omit this field for now as are not exported with previous Pydantic version. TODO: Review if has to be added
+    # datetime: dt.datetime
+    #
     @field_serializer("datetime")
     def serialize_time(self, dt: dt.datetime, _info) -> float:
         return dt.timestamp()