Pin sub-dependecy of clap to be compatible with MSRV

[sirhcel]

Fix building from a fresh start with our current MSRV 1.59.0. There has been an incompatible change with respect to the MSRV in os_str_bytes with the minor version update to 6.6.0.

As of 83fd7fb this fails with:

$ rm -r target Cargo.lock
$ export SERIALPORT_RS_TEST_PORT_1=DUMMY_1
$ export SERIALPORT_RS_TEST_PORT_2=DUMMY_2
cargo +1.59.0 test --features ignore-hardware-tests
error: package `os_str_bytes v6.6.1` cannot be built because it requires rustc 1.61.0 or newer, while the currently active rustc version is 1.59.0

This PR adds a direct dependency to os_str_bytes for tricking the dependency resolution into using a compatible version.

[eldruin]

Hmm, sorry I did not look at this soon enough. There is a conflict now in the Cargo.toml. Could you have a look?

[sirhcel]

Thank you for pointing it out! This was a quick fix.