Update classifiers for pypi. (#907)

Author: janiversen

setup.cfg

@@ -12,14 +12,19 @@ long_description = file: README.rst, CHANGELOG.rst, LICENSE
 url              = 'https://github.com/riptideio/pymodbus/'
 classifiers      = 
     Development Status :: 4 - Beta
-    Programming Language :: Python :: 3.8 :: 3.9 :: 3.10
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     Environment :: Console
-    Framework :: Twisted :: Tornado :: Asyncio
-    Intended Audience :: Developers :: Modbus testers
+    Framework :: Asyncio
+    Intended Audience :: Developers
     License :: OSI Approved :: BSD License
-    Operating System :: OS Independent :: Linux :: Windows :: Mac OS
-    Programming Language :: Python :: 3.8
-    Topic :: System :: Networking :: Utilities :: SCADA :: Modbus
+    Operating System :: OS Independent :: Linux
+    Operating System :: POSIX :: Linux
+    Operating System :: Microsoft :: Windows
+    Operating System :: MacOS
+    Topic :: System :: Networking
+    Topic :: Utilities
 project_urls     =
     Source Code  = https://github.com/riptideio/pymodbus
     Bug Reports  = https://github.com/riptideio/pymodbus/issues