Upgrade urwid and require python 3.9

Because urwid3 required python 3.9, and 3.8 is EOL.

.vermin

@@ -1,4 +1,4 @@
 [vermin]
 only_show_violations = yes
 show_tips = no
-targets = 3.8
+targets = 3.9-

pyproject.toml

@@ -8,7 +8,7 @@ authors = [{ name="Ivan Habunek", email="ivan@habunek.com" }]
 description = "Mastodon CLI client"
 readme = "README.rst"
 license = "GPL-3.0-only"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 dynamic = ["version"]
 
 classifiers = [
@@ -24,7 +24,7 @@ dependencies = [
     "python-dateutil>=2.8.1,<3.0",
     "requests>=2.13,<3.0",
     "tomlkit>=0.10.0,<1.0",
-    "urwid>=2.0.0,<3.0",
+    "urwid>3.0.0,<4.0.0",
     "wcwidth>=0.1.7",
 ]