Improve Vale BadPlurals.yml efficiency

What does this MR do?

This MR improves the efficiency and correctness of Vale's BadPlurals.yml.

• Original (200 steps): \w*\(s\)(?<!http\(s\))
• Proposed (89 steps, regex101): \b\w+\(s\)(?<!http\(s\))

With the proposed regex:

• Vale completes several seconds faster on my machine
• Removes the false positives ## (s) and Do not use **(s)** to make
  • Lines 825 and 827 of doc/development/documentation/styleguide/word_list.md

Explanation of change:

• Inclusion of \b: use a word boundary to enforce longest match
  • Example: for text foobar, \w+ checks f, fo, foo, foob, fooba, and foobar whereas \b\w+ only checks foobar. These are equivalent in this context because Vale only uses the longest match.
• Change * to +: (s) by itself currently does not exist, except in the stylefuide example. (s) may be valid in some future contexts.

Related issues and MRs

Related to !71016 (merged)

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