Upgrade workflow actions to use Node 16

[josecelano]

We have this warning on the CI workflow:

Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: actions/checkout@v2, actions-rs/toolchain@v1, Swatinem/rust-cache@v1, actions-rs/cargo@v1. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/.

For example:

https://github.com/torrust/torrust-tracker/actions/runs/4066640056

I think we need to upgrade workflow actions.