update rust-vmm-ci

The following commits are included in the submodule update:

7e3f307 skip coverage-arm test
cd7096e Enable rust-vmm coverage test in CI
c309d06 buildkite: Move to the rustvmm/dev v4 container
c85a8da buildkite: Remove clippy test on aarch64

Signed-off-by: Andreea Florescu <[email protected]>

Author: andreeaflorescu