Don't require setuptools in dependencies in pyproject.toml

It's not required for production use, only for building.
Instead, add the constraint part to `build_system -> requires` to
save everyone having to ship setuptools in production builds.

Fixes #154.

Author: lewiscollard

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools", "setuptools-scm", "wheel"]
+requires = ["setuptools>=68.2.2", "setuptools-scm", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -9,9 +9,6 @@ description = "Reader for the MaxMind DB format"
 authors = [
     {name = "Gregory Oschwald", email = "[email protected]"},
 ]
-dependencies = [
-    "setuptools>=68.2.2",
-]
 requires-python = ">=3.8"
 readme = "README.rst"
 license = {text = "Apache License, Version 2.0"}