chore(config): remove unnecessary 'frozen' parameter for test

- Simplified app configuration by removing the 'frozen' parameter since it is no longer needed.
- Ensures more flexible handling of config attributes.

api/configs/app_config.py

@@ -27,7 +27,6 @@ class DifyConfig(
         # read from dotenv format config file
         env_file=".env",
         env_file_encoding="utf-8",
-        frozen=True,
         # ignore extra attributes
         extra="ignore",
     )