Drop Python wheel support for Python 3.9

Python 3.9 is EOL.  This loses us support for Debian 11 (oldoldstable),
the default Python on EL 9, and /usr/bin/python3 on macOS.

The minimum supported Python on EL 8 now has a new enough pip.

Signed-off-by: Benjamin Gilbert <bgilbert@cs.cmu.edu>

Author: bgilbert

artifacts/python/README.md

@@ -20,17 +20,13 @@ of OpenSlide.
 Install with `pip install openslide-bin`.  OpenSlide Python ≥ 1.4.0 will
 automatically find openslide-bin and use it.
 
-openslide-bin is available for Python 3.9+ on the following platforms:
+openslide-bin is available for Python 3.10+ on the following platforms:
 
 - Linux aarch64 and x86_64 with glibc 2.28+ (Debian, Fedora, RHEL 8+,
   Ubuntu, many others)
 - macOS 11+ (arm64 and x86_64)
 - Windows 10+ and Windows Server 2016+ (x64)
 
-pip older than 20.3 cannot install openslide-bin, claiming that it `is not a
-supported wheel on this platform`.  On platforms with these versions of pip
-(RHEL 8), upgrade pip first with `pip install --upgrade pip`.
-
 ## Using
 
 Use OpenSlide via [OpenSlide Python][].  The OpenSlide Python

artifacts/python/pyproject.in.toml

@@ -19,7 +19,6 @@ classifiers = [
     "Operating System :: POSIX :: Linux",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
@@ -28,7 +27,7 @@ classifiers = [
     "Topic :: Scientific/Engineering :: Bio-Informatics",
     "Typing :: Typed",
 ]
-requires-python = ">= 3.9"
+requires-python = ">= 3.10"
 
 [project.urls]
 Homepage = "https://openslide.org/"