Remove cython from install requires

[trxcllnt]

Cython is a build-only dependency, so this PR removes Cython from the install_requires list of the hdbscan package.

setup.py reads requirements.txt to populate its runtime requirements, and requirements.txt incldues cython. So removing it from requirements.txt should be sufficient to fix this.

I can make a separate requirements-build.txt if the maintainers prefer using a requirements file for build dependencies.

[jakirkham]

Thanks Paul! 🙏

Had a question below

[jakirkham]

Should we change this to build with Cython 3+ and NumPy 2+ as well?

hdbscan/pyproject.toml

Lines 1 to 7 in c201b2e

	[build-system]
	requires = [
	"setuptools",
	"wheel",
	"cython<4",
	"numpy<3"
	]

So...

 [build-system]
 requires = [
   "setuptools",
   "wheel",
-  "cython<4",
+  "cython>=3,<4",
-  "numpy<3"
+  "numpy>=2,<3"
 ]

[lmcinnes]

Thank you!

[jakirkham]

Thank you both! 🙏