Inform that users can safely ignore {registration,reset password} email if the actions wasn't initiated by them.

A couple of weeks ago, we had a request to undo a registration to mentors.

We should add a note in the registration/reset password email indicating that it can be safely ignored if the action wasn't initiated by them.

The paragraph could be:

For subscription:

If you didn't create an account on %(sitename)s, you can safely ignore this email.

For password reset:

If you didn't request this password reset, you can safely ignore this email.