bug(settings): Fix rate-limit rule on mfa verify code

[dschom]

Because

• The rule name was incorrect for the mfa verify otp code rate limit

This pull request

• Fixes the rule name

Issue that this pull request solves

Closes: FXA-12471

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

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