Fix mautrix-python import error.

Because of mautrix-python library [API Changes](https://github.com/tulir/mautrix-python/commit/04d2ae4c3d4db5f8798f4f844caafb5d00606507). Database migration script is broken.

mautrix_telegram/scripts/dbms_migrate/__main__.py

@@ -24,7 +24,8 @@ def log(message, end="\n"):
 
 
 def connect(to):
-    from mautrix.bridge.db import Base, RoomState, UserProfile
+    from mautrix.util.db import Base
+    from mautrix.bridge.db import RoomState, UserProfile
     from mautrix_telegram.db import (Portal, Message, UserPortal, User, Contact, Puppet, BotChat,
                                      TelegramFile)