Update AccountReset email

[brynwhyman]

Overview

The email sent when an Admin initiates an account reset could be improved so that if the user was not expecting it, they're advised on what can be done, i.e 'ignore it'.

Change request

• Add an additional line to the email template:
  If you did not make this request, please ignore this email.

Email template: https://github.com/silverstripe/silverstripe-mfa/blob/master/templates/SilverStripe/MFA/Email/AccountReset.ss

Extra request

• I think it makes sense to make the same change to the Forgot Password email template in Framework as well. https://github.com/silverstripe/silverstripe-framework/blob/4/templates/SilverStripe/Control/Email/ForgotPasswordEmail.ss

[brynwhyman]

Given this matches the existing Forgot Password template, I'm not adding this to the 'Phase 1 release', although it would be good to squeeze in if we can