Revert "packaging: restore Python 3.8 and 3.9"

This reverts commit 020d7fe.

Author: Guts

setup.py

@@ -78,7 +78,7 @@ def load_requirements(requirements_files: Path | list[Path]) -> list:
     # run
     entry_points={"mkdocs.plugins": ["rss = mkdocs_rss_plugin.plugin:GitRssPlugin"]},
     # dependencies
-    python_requires=">=3.8, <4",
+    python_requires=">=3.10, <4",
     extras_require={
         # tooling
         "dev": load_requirements(HERE / "requirements/development.txt"),
@@ -92,8 +92,6 @@ def load_requirements(requirements_files: Path | list[Path]) -> list:
         "Intended Audience :: Developers",
         "Intended Audience :: Information Technology",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.8",
-        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",