Bump embedded-hal to rc 3

[tommy-gilligan]

No description provided.

[eldruin]

Thanks!
Could you update the changelog as well?

[tommy-gilligan]

I updated the changelog. I think it maybe makes sense to squash the eh update lines but I didn't want to presume (so no squashing unless you say so)

[eldruin]

Thanks!
Please do squash them.

[tommy-gilligan]

Looks like a transient network failure on CI

[eldruin]

Hmm, could you add sudo apt-get update to the CI here like this?:

run: |
    sudo apt-get update
    sudo apt-get install -y libc6-armhf-cross libc6-dev-armhf-cross gcc-arm-linux-gnueabihf

[eldruin]

Thank you!