Remove python-dotenv from the dependencies

zsh-dotenv automatically loads the environment variables upon entering
the project's root.

src/urban_meal_delivery/configuration.py

@@ -13,11 +13,6 @@ import random
 import string
 import warnings
 
-import dotenv
-
-
-dotenv.load_dotenv()
-
 
 def random_schema_name() -> str:
     """Generate a random PostgreSQL schema name for testing."""