Update rustsec v0.31

[jayvdb]

Fixes #804

See https://github.com/rustsec/rustsec/releases/tag/rustsec%2Fv0.31.0

[jayvdb]

ping @Jake-Shadle

[djc]

There's really no need to mention people -- people watch their repos and get notifications anyway.

[tisonkun]

There's really no need to mention people -- people watch their repos and get notifications anyway.

Not quite. Subscription sends emails to [email protected] while mention would add user's personal email address in cc (as well as [email protected]). People (like me) may use speicial rules to highlight emails that directly send to the personal mailbox.