RUSTSEC-2019-0031: spin is no longer actively maintained

[github-actions]

spin is no longer actively maintained

Details
Status	unmaintained
Package	spin
Version	0.5.2
URL	mvdnes/spin-rs@7516c80
Date	2019-11-21
Unaffected versions	> 0.5.2

The author of the spin crate does not have time or interest to maintain it.

Consider lock_api (a subproject of
parking_lot) as an alternative which also supports no_std environments.

See advisory page for additional details.