Ignore some links that can't be checked in CI

* Skip all .onion URLs since Tor isn't set up
* The GNOME website returns a 403 from cloud networks, including the one
  GitHub Actions runs from.
* Same with the Lenovo support website, except it just times out.

docs/conf.py

@@ -239,3 +239,9 @@
 # The default is to use Python’s global socket timeout, which may be `None`.
 # This can cause CI jobs to time out.
 linkcheck_timeout = 30
+
+linkcheck_ignore = [
+    r"http://.*\.onion/.*",
+    "https://www.gnome.org/", # returns 403 from cloud networks
+    "https://support.lenovo.com", # timeout from cloud networks
+]