Removed reference to deleted documentation and added language about updating to landing page

[dylanbuel]

Hello all. This is a very small PR to save people some confusion I had today reading over your documentation.

The document installing-from-release-windows.md was removed in PR #675 but was still included in the summary and referenced under the installation landing page

Pull Request Checklist

• The Rayhunter team has recently expressed interest in reviewing a PR for this. If not, this PR may be closed due our limited resources and need to prioritize how we spend them.
• [ x ] Added or updated any documentation as needed to support the changes in this PR.
• [ x ] Code has been linted and run through cargo fmt
• [ x ] If any new functionality has been added, unit tests were also added
• [ x ] ./CONTRIBUTING.md has been read

[untitaker]

thank you!