Update beta message for 2.10.4beta.
Update beta message for 2.10.4beta.

UweTrottmann/SeriesGuide,UweTrottmann/SeriesGuide,epiphany27/SeriesGuide,r00t-user/SeriesGuide,artemnikitin/SeriesGuide,hoanganhx86/SeriesGuide,0359xiaodong/SeriesGuide