build: Drop support for Python 3.8

Author: pawamoy

pyproject.toml

@@ -8,7 +8,7 @@ description = "MkDocs plugin to generate a manpage from the documentation site."
 authors = [{name = "Timothée Mazzucotelli", email = "dev@pawamoy.fr"}]
 license = {text = "ISC"}
 readme = "README.md"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 keywords = []
 dynamic = ["version"]
 classifiers = [
@@ -17,7 +17,6 @@ classifiers = [
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",