Temporarily ignore Nokogiri CVE-2016-4658

See https://gitlab.com/gitlab-org/gitlab-ce/issues/29992 for progress on
updating this gem. In the meantime, we can't do anything about it
quickly, so we'll ignore the CVE in `bundle-audit`

.gitlab-ci.yml

@@ -312,7 +312,7 @@ bundler:audit:
     - master@gitlab/gitlabhq
     - master@gitlab/gitlab-ee
   script:
-    - "bundle exec bundle-audit check --update"
+    - "bundle exec bundle-audit check --update --ignore CVE-2016-4658"
 
 migration paths:
   stage: test