CI: AppVeyor builds using Rust 1.58.0 are broken

[thomasjfox]

AppVeyor builds using Rust 1.58.0 on the CI system are broken.

cargo 1.58.0 (7f08ace4f 2021-11-24)
cargo build %RELEASE% --verbose
    Updating crates.io index
error: failed to select a version for the requirement `rpassword = "^7.0.0"`
candidate versions found which didn't match: 6.0.1, 6.0.0, 5.0.1, ...
location searched: crates.io index

It complains about a missing rpassword 7.0.0 dependency and I think it's related to this: rust-lang/cargo#10623

If support for the old compiler should be kept, we could try to vendorize the rpassword crate.

Though the "cargo" crate is probably the next candidate that will cause trouble. IIRC during research for the openssl issue in #491, the MSRV for cargo 0.64.0 was Rust 1.60.0.