Limit numpy version for Windows only

Github Action tests found a numerical difference on one test, but only
on Windows and unrelated to code changes. Numpy update is a likely
suspect, and pinning seems to prevent the issue. Make this pin
OS-dependent for now, and see what happens. Will be interesting to see
if it also applies to Conda builds...

setup.py

@@ -139,7 +139,7 @@ def run_setup():
         include_package_data=True,
         install_requires=[
             'packaging',
-            'numpy>=1.24.0,<2.1',
+            'numpy>=1.24.0,<2.1' if "win" in platform else 'numpy>=1.24.0',
             'scipy>=1.10',
             'seekpath>=1.1.0',
             'spglib>=1.9.4',