Update Windows installation instructions

We've re-enabled Windows builds so building from source on Windows is no longer needed. `foundryup` does **not** work on Windows, though, so the binaries manually have to be downloaded from Foundry's releases page.

Start by locating the Windows installation instructions in the book and compare them with the current Foundry releases page. Update the guidance so Windows users are directed to download binaries manually rather than build from source or use foundryup; done when the instructions reflect the re-enabled Windows builds.

Written by the indexing model from the issue text.