chore: adjust classifiers

Author: Midnighter

setup.cfg

@@ -9,13 +9,12 @@ classifiers =
     Intended Audience :: Developers
     License :: OSI Approved :: Apache Software License
     Natural Language :: English
-    Operating System :: MacOS :: MacOS X
-    Operating System :: Microsoft :: Windows :: Windows 10
-    Operating System :: POSIX
-    Programming Language :: Python :: 3.5
+    Operating System :: OS Independent
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
+    Topic :: Utilities
 license = Apache-2.0
 description = List a package's direct dependencies and their versions.
 long_description = file: README.rst