Remove cmake dependency in pyproject.toml

While cmake is a dependency needed to build ninja, there are many ways to install it on a system. Forcing the cmake python distribution to be used is not appropriate here.

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "scikit-build", "cmake"]
+requires = ["setuptools>=42", "wheel", "scikit-build"]
 build-backend = "setuptools.build_meta"