RUSTSEC-2021-0139: ansi_term is Unmaintained

[github-actions]

ansi_term is Unmaintained

Details
Status	unmaintained
Package	ansi_term
Version	0.12.1
URL	ogham/rust-ansi-term#72
Date	2021-08-18

The maintainer has adviced this crate is deprecated and will not
receive any maintenance.

The crate does not seem to have much dependencies and may or may not be ok to use as-is.

Last release seems to have been three years ago.

Possible Alternative(s)

The below list has not been vetted in any way and may or may not contain alternatives;

• anstyle
• nu-ansi-term
• yansi

See advisory page for additional details.

[jim-signal]

This is a dependency of a dependency (Structopt) that we'll soon be replacing anyway. And the specific issue doesn't affect us and is therefore tolerable.