Remove unused python-dotenv dependency

load_dotenv() was called, but no setting was ever read from a .env
file. Drop it from the code, pyproject.toml, PKGBUILD and README.

simple_backup/simple_backup.py

@@ -34,8 +34,6 @@ from tempfile import mkstemp
 from getpass import GetPassWarning, getpass
 from glob import glob
 
-from dotenv import load_dotenv
-
 try:
     import paramiko
     from paramiko import RSAKey, Ed25519Key, ECDSAKey, DSSKey
@@ -53,7 +51,6 @@ except ImportError:
     dbus = None
 
 
-load_dotenv()
 logging.getLogger().setLevel(logging.DEBUG)
 logger = logging.getLogger(os.path.basename(__file__))
 c_handler = StreamHandler()