remove python 3.8 support (#10077)

fixes https://github.com/certbot/certbot/issues/10035. you can compare
this to the PR that did this for python 3.7 at
https://github.com/certbot/certbot/pull/9792

i agree with erica's comment at
https://github.com/certbot/certbot/issues/10035#issuecomment-2452212686,
but felt this PR was already getting pretty large so i did that in a
second PR at https://github.com/certbot/certbot/pull/10076

certbot-dns-rfc2136/setup.py

@@ -7,7 +7,10 @@ from setuptools import setup
 version = '3.1.0.dev0'
 
 install_requires = [
-    'dnspython>=1.15.0',
+    # This version was chosen because it is the version packaged in RHEL 9 and Debian unstable. It
+    # is possible this requirement could be relaxed to allow for an even older version of dnspython
+    # if necessary.
+    'dnspython>=2.6.1',
 ]
 
 if os.environ.get('SNAP_BUILD'):
@@ -38,7 +41,7 @@ setup(
     author="Certbot Project",
     author_email='certbot-dev@eff.org',
     license='Apache License 2.0',
-    python_requires='>=3.8',
+    python_requires='>=3.9',
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Environment :: Plugins',
@@ -47,7 +50,6 @@ setup(
         'Operating System :: POSIX :: Linux',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',