Fix BaseSettings import for pydantic v2 (#1798)

* Bumped preflight version to 1.9.7

* Fix BaseSetting import for pydantic v2 in generate_dotenv

* Master preflight version.

hack/generate_dotenv.py

@@ -13,7 +13,7 @@
 import os
 
 from typing import List, Tuple, Type
-from pydantic import BaseSettings
+from pydantic_settings import BaseSettings
 
 from mlserver.settings import Settings, ModelSettings, ModelParameters
 from mlserver.cli.serve import DEFAULT_SETTINGS_FILENAME