https://www.rust-lang.org/learn/get-started says `curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs/ | sh`, but https://forge.rust-lang.org/infra/other-installation-methods.html says `curl https://sh.rustup.rs/ -sSf | sh`. Which is recommended? Why do they say different commands?