Update briefs word count limit

[nmorduch]

• Raise limit because our word count runs higher than word processors' (so people sometimes hit our limit even when they've carefully edited to be within the limit)
• Stop showing our word count in the error so that the raised limit doesn't just become the new limit
  • Ideally have it still in the html, just commented out or similar (for our troubleshooting)
• Ideally have it so that for superusers the word count limit is just a warning, not a hard limit.