Remove setuptools-rust and milksnake mentions from readme

Maturin initially started out of dissatisfaction about what UX was possible with setuptools-rust. Maturin has grown into much than that, supports many more features than both setuptools-rust and milksnake, is not really zero config anymore (with the pyproject.toml build backend) and should present itself by its strengs rather than in comparison with other tools. So i'm replacing the old initial release pitch with something more modern.

README.md

@@ -9,10 +9,8 @@ _formerly pyo3-pack_
 [![FreeBSD](https://img.shields.io/cirrus/github/PyO3/maturin/main?logo=CircleCI&style=flat-square)](https://cirrus-ci.com/github/PyO3/maturin)
 [![Chat on Gitter](https://img.shields.io/gitter/room/nwjs/nw.js.svg?logo=gitter&style=flat-square)](https://gitter.im/PyO3/Lobby)
 
-Build and publish crates with pyo3, rust-cpython, cffi and uniffi bindings as well as rust binaries as python packages.
-
-This project is meant as a zero configuration replacement for [setuptools-rust](https://github.com/PyO3/setuptools-rust) and [milksnake](https://github.com/getsentry/milksnake).
-It supports building wheels for python 3.7+ on windows, linux, mac and freebsd, can upload them to [pypi](https://pypi.org/) and has basic pypy and graalpy support.
+Build and publish crates with pyo3, rust-cpython, cffi and uniffi bindings as well as rust binaries as python packages with minimal configuration.
+It supports building wheels for python 3.8+ on windows, linux, mac and freebsd, can upload them to [pypi](https://pypi.org/) and has basic pypy and graalpy support.
 
 Check out the [User Guide](https://maturin.rs/)!