Add a newline character to end of pyproject.toml

Is this TOML file actually needed?

I'd prefer to remove it since it does so little, and stands out so
prominiently.

Author: ingydotnet

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
 requires = ["setuptools", "wheel", "Cython"]
-build-backend = "setuptools.build_meta"
+build-backend = "setuptools.build_meta"