Ignore CA Certificate link for linkcheck

This has consistently returned 403 in GitHub Actions workflow, but
does succeed when running linkcheck locally. Ignoring link for now and
we can revisit later.

src/conf.py

@@ -103,6 +103,8 @@
      # these URLs block the client the linkchecker uses
      r'^https://www\.pnas\.org/doi/10\.1073/pnas\.1507071112',
      r'^https://www\.ncbi\.nlm\.nih\.gov/books/NBK25501',
+     # This URL returns 403 in GH Actions, but succeeds locally.
+     r'^https://wiki\.mozilla\.org/CA/Included_Certificates',
      # we specifically use this as an example of a link that _won't_ work
      r'^https://nextstrain\.org/ncov/gisaid/21L/global/6m/2024-01-10',
 ]