update dependencies
update tokio following RUSTSEC-2021-0124. Also update other dependencies because it can't harm to be a little more up to date (or can it?).
note: nightly CI is failing because vendored/bundled openssl does not support "RC2-40-CBC". Sounds old and deprecated. Shall I try to create a new .pfx with newer crypto, or downgrade openssl-src back to something that support RC2?