correct and simplify metadata in setup.cfg.in

Wrap/Python/setup.cfg.in

@@ -46,19 +46,14 @@ project_urls =
 classifiers =
     Programming Language :: C++
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.8
-    Programming Language :: Python :: 3.9
-    Programming Language :: Python :: 3.10
+    Operating System :: Linux
+    Operating System :: macOS
     Operating System :: Microsoft :: Windows
-    Operating System :: POSIX
-    Operating System :: Unix
-    Operating System :: MacOS
     Development Status :: 5 - Production/Stable
     Topic :: Scientific/Engineering :: Physics
     License :: OSI Approved :: GNU General Public License (GPL)
 
-platforms = Windows, Linux, Mac OS-X, Unix
+platforms = Linux, macOS, Windows
 
 keywords =
     neutron