chore: proper current_app.config proxy usage (#34345)

Co-authored-by: Claude <noreply@anthropic.com>

superset/databases/ssh_tunnel/models.py

@@ -18,7 +18,6 @@
 from typing import Any
 
 import sqlalchemy as sa
-from flask import current_app
 from flask_appbuilder import Model
 from sqlalchemy.orm import backref, relationship
 from sqlalchemy.types import Text
@@ -32,8 +31,6 @@ from superset.models.helpers import (
     ImportExportMixin,
 )
 
-app_config = current_app.config
-
 
 class SSHTunnel(AuditMixinNullable, ExtraJSONMixin, ImportExportMixin, Model):
     """