Create test for bad pluralization

We don't want words written with an '(s)' to indicate possible
pluralization. Just write it as a plural already, please and thanks.

doc/.vale/gitlab/BadPlurals.yml

+---
+# Suggestion: gitlab.BadPlurals
+#
+# Don't write plural words with the '(s)' construction. "HTTP(S)" is acceptable.
+#
+# For a list of all options, see https://docs.errata.ai/vale/styles
+extends: existence
+message: 'Rewrite "%s" to be plural, without parentheses.'
+link: https://docs.gitlab.com/ee/development/documentation/styleguide/word_list.html
+level: warning
+scope: raw
+ignorecase: true
+raw:
+  - '\w*\(s\)(?<!http\(s\))'