Remove Cigna from password rules

[carlylemiii]

I propose removing the rule for Cigna, as they have updated their requirements to be very general and any password manager shouldn't have a problem generating passwords anymore. The current rule is more harmful than helpful, as it limits things to specific characters and under 12 total.

Overall Checklist

• [x] I agree to the project's Developer Certificate of Origin
• [x] The top-level JSON objects are sorted alphabetically
• [x] There are no open pull requests for the same update

for password-rules.json

• [ ] The given rule isn't particularly standard and obvious for password managers
• [ ] Generated passwords have been tested from this rule using the Password Rules Validation Tool
• [x] Information has been included about the website's requirements (eg. screenshots, error messages, steps during experimentation, etc.)
• [x] The PR isn't documenting something that would be a common practice among password managers (e.g. minimal length of 6)