Update fuelup version in installation docs

[jintukumardas]

I noticed that the installation docs still mention fuelup 0.21.0 (see screenshot) while the latest version is 0.27.4.

It might be worth updating the doc to avoid confusion for new users.

Also wondering: is there an API or endpoint (e.g., crates.io release info, GitHub releases) that could be fetched and cached so the docs always display the current latest fuelup version, instead of having to manually update each time?