py-dotenv: updated to 0.21.1

0.21.1

Added
* Use Python 3.11 non-beta in CI
* Modernize variables code
* Modernize main.py and parser.py code
* Improve conciseness of cli.py and __init__.py
* Improve error message for `get` and `list` commands when env file can't be opened
* Updated Licence to align with BSD OSI template

Fixed
* Fix Out-of-scope error when "dest" variable is undefined
* Fix IPython test warning about deprecated `magic`
* Fix type hint for dotenv_path var, add StrPath alias

(adam)