Update Download location

[kescobo]

This PR currently just changes the help message about where to download - the previous link gets redirected to the main YNAB page, not the YNAB 4 download page.

I wasn't sure how to change the automatic download, which doesn't currently work. It looks like it's designed to download a YAML file that contains download URLs for different versions, and then sets DOWNLOAD_LOCATION from that file, but since there's no more development of YNAB4 happening, I don't think that's necessary any more. But I don't know how to fix it because I don't know perl. But the correct download location for the .exe file is now https://www-assets.youneedabudget.com/ynab4/YNAB+4_4.3.857_Setup.exe