Update github action `actions-rs/toolchain` when its update to using node-16

[FirelightFlagboy]

Github started deprecation of node-12 that is EOL.
We have actions-rs/toolchain that use that version.
We need to wait for them to update the node that they're using.
Here are the item that track this change:

• Node.JS 12 deprecation on GitHub Actions actions-rs/toolchain#219
• Update the action to run on Node 16 actions-rs/toolchain#220

After one of those is resolve (and most importantly, they aren't using node-12), we can update our action setup-rust in .github/actions/setup-rust