PEP 639 license information

Declare licenses using these two fields, as per PEP 639:
* license:       SPDX license expression
* license-files: list of license file glob patterns

The build system maturin ≥ 1.9 supports PEP 639, which means the proper
licensing metadata should be included in packages and seen by PyPI:
	https://www.maturin.rs/changelog.html

For tools such as pip-licenses that do not understand PEP 639 yet, keep
the redundant classifier until they catch up.

Author: DimitriPapadopoulos

pyproject.toml

@@ -9,7 +9,8 @@ description = "An extremely fast Python linter and code formatter, written in Ru
 authors = [{ name = "Astral Software Inc.", email = "[email protected]" }]
 readme = "README.md"
 requires-python = ">=3.7"
-license = { file = "LICENSE" }
+license = "MIT"
+license-files = { "LICENSE" }
 keywords = [
     "automation",
     "flake8",