MNT: Apply repo-review rule PP002

PP002: Has a proper build-system table

Must have `build-system.requires` and `build-system.backend`.
Both should be present in all modern packages.

Author: DimitriPapadopoulos

pyproject.toml

@@ -1,5 +1,6 @@
 [build-system]
 requires = ["setuptools >= 30.3.0", "wheel"]
+build-backend = "setuptools.build_meta"
 
 [tool.black]
 skip-string-normalization = true