Fix broken FileZilla package: change URL

Your FileZilla package is not updating anymore, because the installer (starting from 3.9.0) is now only downloadable via SourceForge. As you probably know, SourceForge is a bit tricky to use with Ketarin, because Ketarin lacks of following HTTP 301/302 redirects which are used there.

I had to “misuse” the `{{DownloadUrlx64}}` substitution variable as 32-bit download URL, otherwise the package would contain a specific mirror URL, which is bad (not all mirrors aren’t always online and some are slow sometimes).

No worries about the adware that was bundled with the FileZilla installer on Windows some time ago. The installer is now adware-free.
Indeed. The only value that can be passed is `{{DownloadUrlx64}}`. That’s the reason why I “abuse” it here.

In [my ffdshow package](https://github.com/TomOne/chocolatey-packages/blob/master/automatic/ffdshow/tools/chocolateyInstall.ps1) I had to construct a PS hash table in Ketarin containing two URLs and pass them using `{{DownloadUrlx64}}`. Not nice and clean, but it works.

Of course it would be better if it were possible to pass other values from Ketarin to chocopkgup.

Are you going to merge this PR? I’m afraid that currently we don’t have better options to make the automatic package for FileZilla work again.