Revert "Fix/attribute error (#1812)" (#1871)

This reverts commit 6cce9c3c28b37774c16ba5b2da5d8cd423f8922a.

opendevin/server/session/msg_stack.py

@@ -99,7 +99,7 @@ class MessageStack:
                 new_data = {}
                 for sid, msgs in data.items():
                     if sid != del_sid:
-                        new_data[sid] = [Message.from_dict(msg) for msg in msgs]
+                        new_data[sid] = msgs
                 # Move the file pointer to the beginning of the file to overwrite the original contents
                 file.seek(0)
                 # clean previous content