use one feedz source for both libvlc and libvlcsharp preview packages

Use one feed for all platforms libvlc preview builds

fixes WACK

[skip ci]

see the one from VLC

Binaries taken from this build https://code.videolan.org/videolan/vlc-winrt/pipelines/10590
The ones from 3.0.8 release were deleted from the CI (not kept for ever),
the 3.x libvlc branch is faily stable,
vlc-winrt does not get many updates,
and 3.0.9 is coming up,

so I took the liberty to push this build.

Fixes videolan/LibVLCSharp#241

Previous one went offline