Fix macOS PyPI classifier

Use the valid MacOS X Trove classifier suggested in review while keeping the SPDX license form that passes the package build.

Author: astomodynamics

pyproject.toml

@@ -16,7 +16,7 @@ classifiers = [
   "Development Status :: 3 - Alpha",
   "Intended Audience :: Science/Research",
   "Operating System :: Microsoft :: Windows",
-  "Operating System :: MacOS",
+  "Operating System :: MacOS :: MacOS X",
   "Operating System :: POSIX :: Linux",
   "Programming Language :: C++",
   "Programming Language :: Python :: 3",