fix: update workflow actions

[ThexXTURBOXx]

See here for more details

[oSumAtrIX]

Please elaborate the changes made to the workflow file here.

[ThexXTURBOXx]

actions-rs is pretty much abandoned.
That's why I forked the toolchain action myself and updated its components.
cargo was updated by another user a while ago.
Because of this, the repos needed to be switched.

[oSumAtrIX]

Before using your fork, I would suggest to PR the changes from your fork. It is unknown wether you will continue to maintain your fork or drop support at some time, while upstream should be guaranteed to be updated if absolutely necessary.

[ThexXTURBOXx]

A PR was already created: actions-rs/toolchain#224
To be exact, multiple PRs already exist for quite a long time, but noone merged them since 2020.
Since Node.js 12 actions could be disabled at any point, it is advisable to use my fork at least as a temporary solution in order to guarantee CI to work properly without breaks.