RUSTSEC-2024-0370: proc-macro-error is unmaintained

[vsirivol]

This repo is using proc-macro2 v1.0.71 and this is causing the issue.

proc-macro-error is unmaintained and is updated to proc-macro-error2: jbaublitz/getset#94

proc-macro2 v1.0.89 has the updated code.

[palfrey]

proc-macro2 can be upgraded in something that depends on this, and now #118 is in, we know that upgrade will still be safe. I don't feel the need to upgrade the dependency here, as we're not blocking other packages from doing that upgrade while using serial_test, especially as we don't use proc-macro-error directly here.

[vsirivol]

Thanks for addressing proc-macro2 upgrade by adding the new step in workflow. But I am a little confused because I don't see that the version update for proc-macro2 is done in the Cargo.lock file. Also I believe according to the workflow trigger, it has to update when there is a push, pull or a crone job that runs every month.

Please feel to correct me if I am wrong or if it takes a little more time before the lock file is updated after pushing the update.