Fix build tools 2019 link (iron-fish#602)

The original link doesn't have a download for the 2019 build tools, only Visual Studio as a whole. The new link takes you to a section that has a direct link to the latest 2019 build tools version.

Co-authored-by: Derek Guenther <[email protected]>

Author: floofy-moo

README.md

@@ -16,7 +16,7 @@ See https://ironfish.network
 1. Install [Rust](https://www.rust-lang.org/learn/get-started).
 1. Install [Yarn](https://classic.yarnpkg.com/en/docs/install).
 1. Windows:
-   1. Install [Build Tools for Visual Studio 2019](https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2019), including the C++ Build Tools and the Windows 10 SDK, for Rust.
+   1. Install [Build Tools for Visual Studio 2019](https://docs.microsoft.com/en-us/visualstudio/releases/2019/history#release-dates-and-build-numbers), including the C++ Build Tools and the Windows 10 SDK, for Rust.
    1. Rust builds also require installing [MinGW-w64 via win-builds](http://win-builds.org/doku.php/download_and_installation_from_windows).
       1. Choose `Native Windows`, `x86_64`, choose an empty directory, and click OK.
       1. On the next screen, click `Process`.