Replace `platforms` with `current_platform`
Created by: ascjones
Supersedes #531.
https://github.com/rustsec/rustsec/pull/516 mentions that current_platform
supersedes this functionality in the move from 2.0 to 3.0.
Created by: ascjones
Supersedes #531.
https://github.com/rustsec/rustsec/pull/516 mentions that current_platform
supersedes this functionality in the move from 2.0 to 3.0.