coreos-base/ue-rs: bump h2, mio

Update to 9b6ddb0226208450bcef9da4ac5ba8bc2a47a87c (2024-04-05), mainly
to address security issues in Rust crates.

Pulls in:
flatcar/ue-rs#51
flatcar/ue-rs#52
flatcar/ue-rs#53
flatcar/ue-rs#54

Author: dongsupark