[Virtio-fs] [virtiofsd] MR merged: Update virtio-queue and vhost-user-backend deps

[virtiofs-bot at sinrega.org]

There are new releases of virtio-queue (0.4.0) and
vhost-user-backend (0.5.0), update our dependencies to use them.

This time, the API has stayed stable and we don't need any other
changes than bumping their versions in Cargo.toml.

Signed-off-by: Sergio Lopez <slp at redhat.com>
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https://gitlab.com/virtio-fs/virtiofsd/-/merge_requests/126