Suggestion: Delegate Rustup's installation instructions to Rustup's docs

[rami3l]

I'm currently doing issue triaging for the Rustup project, and I've found out that when it comes to Rust installation instructions (esp. for newcomers), some will link to https://forge.rust-lang.org/infra/other-installation-methods.html, while others will point to https://rust-lang.github.io/rustup/installation/index.html.

I have realized that the scope of these two pages are slightly different, but regarding the section on Rustup's installation (which is a bit outdated already), I think maybe https://forge.rust-lang.org/infra/other-installation-methods.html#other-ways-to-install-rustup should be removed in favor of a link to Rustup's docs at https://rust-lang.github.io/rustup/installation/other.html. That way, we can maintain a single source of truth.

How does that sound?