Replace mentions on Python 3.8 with 3.9 (follow-up to #411)

Author: achimnol

docs/index.rst

@@ -6,7 +6,7 @@
 aiomonitor's documentation!
 ===========================
 
-**aiomonitor** is Python 3.8+ module that adds monitor and cli capabilities
+**aiomonitor** is Python 3.9+ module that adds monitor and cli capabilities
 for :mod:`asyncio` application. Idea and code borrowed from curio_ project.
 Task monitor that runs concurrently to the :mod:`asyncio` loop (or fast drop in
 replacement uvloop_) in a separate thread. This can inspect the loop and

setup.cfg

@@ -14,7 +14,6 @@ classifiers =
     License :: OSI Approved :: Apache Software License
     Intended Audience :: Developers
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11