Smtpdfix

- Removes redundant `smtpdfix.typing` module.
- Drop support for PyPy 3.7 from testing.
- Fixes an issue where `tests` would be installed as a package by pip. [Issue 328](https://github.com/bebleo/smtpdfix/issues/328) reported by [thedamnedrhino](https://github.com/thedamnedrhino).

**Includes Potentially Breaking Changes:**

Previously `smtpdfix` would load a `.env` file automatically using `python-dotenv`. This behaviour has been corrected and .env files must be loaded separately.

Previous versions used port 8025 by default, as of version 0.5.0 a random port is used instead.

- As of version 0.5.0 Smtpdfix no longer uses `python-dotenv` to load a `.env` file by default. [Issue 274](https://github.com/bebleo/smtpdfix/274) reported by [Emmanuel Belair (e-belair)](https://github.com/e-belair)
- A random unused port is used instead of the default 8025 port. [Issue 820](https://github.com/bebleo/smtpdfix/issues/280) reported by [Éloi Rivard](https://github.com/azmeuk)
- Replaced the deprecated key `license_file` with `license_files` as per warning during build.

+ Pin cryptography version for PyPy to mitigate issues with cryptography 40.0.0 and later.

+ Adds support for python 3.11.
+ Corrects an error related to `aiomsmtpd` that prevented StartTLS commands from working correctly. Issue 227

**Includes Potentially Breaking Changes**

+ Support has been dropped for python 3.6.
+ The `certs.generate_certs` method has been removed from the public API.

**Full Changelog**: [CHANGELOG.md](https://github.com/bebleo/smtpdfix/blob/3f63ad6525ad27c9fba66b9088089d0aefb18ec1/docs/CHANGELOG.md)

Fixes install issues caused by a newline in short description.