An old account of yours presumably - don't action anything nothing would be changed.
I have seen a few instances of this, I have had one myself (in almost nine years using the forums) and I don't really know why they occur.
One possibility is someone typed their user name incorrectly and hit on one previously created, now the password that they enter would fail and they request a password change. The problem being that goes to the email address of the correct user (you) who knows nothing about it.
Generally I don't see this as malicious, e.g. trying to take over an account because of that action the email is sent to the account holder and they would have previously had to have access to your email account to receive the email.
