procinfo is unmaintained and has not been updated in 5+ years.

It will soon cause us to be unable to upgrade Rust:

warning: the following packages contain code that will be rejected by a future version of Rust: nom v2.2.1

:; cargo tree -i [email protected]
nom v2.2.1
└── procinfo v0.4.2
    └── linkerd-system v0.1.0 (/workspaces/dev/repos/linkerd2-proxy/linkerd/system)

We need to either replace or fork/update our procinfo dependency.