Fix migration error

Author: lulunac27a

migrations/env.py

@@ -4,10 +4,11 @@
 from flask import current_app
 
 from alembic import context
+from alembic.config import Config
 
 # this is the Alembic Config object, which provides
 # access to the values within the .ini file in use.
-config: context.Config = context.config
+config: Config = context.config
 
 # Interpret the config file for Python logging.
 # This line sets up loggers basically.