Make the pyproject.toml classifiers reflect the Python 3.9 -> 3.10 upgrade

Author: JoostGevaert

pyproject.toml

@@ -55,7 +55,6 @@ classifiers = [
     "Topic :: Scientific/Engineering",
     "Topic :: Scientific/Engineering :: GIS",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",