Fix `clippy::single_char_pattern`
Created by: cmichi
See here for the complete error output which is currently happening on master
: https://gitlab.parity.io/parity/cargo-contract/-/jobs/1284437.
Created by: cmichi
See here for the complete error output which is currently happening on master
: https://gitlab.parity.io/parity/cargo-contract/-/jobs/1284437.