[bestsource provider] Remove VariableFormat parameter

This [commit](vapoursynth/bestsource@633d6e8#diff-fe0470628acf368c8971852850ca82394169b0fd8a64c78426663f21ee0ef2a2) added the ViewID parameter in videosource.h

Let's set it to 0 since we don't support spatial videos.

src/video_provider_bestsource.cpp

@@ -116,7 +116,7 @@ BSVideoProvider::BSVideoProvider(agi::fs::path const& filename, std::string cons
 		ps->SetTitle(from_wx(_("Indexing")));
 		ps->SetMessage(from_wx(_("Decoding the full track to ensure perfect frame accuracy. This will take a while!")));
 		try {
-			bs = agi::make_unique<BestVideoSource>(filename.string(), "", 0, static_cast<int>(track_info.first), OPT_GET("Provider/Video/BestSource/Threads")->GetInt(), 1, provider_bs::GetCacheFile(filename), &bsopts, [=](int Track, int64_t Current, int64_t Total) {
+			bs = agi::make_unique<BestVideoSource>(filename.string(), "", 0, static_cast<int>(track_info.first), 0, OPT_GET("Provider/Video/BestSource/Threads")->GetInt(), 1, provider_bs::GetCacheFile(filename), &bsopts, [=](int Track, int64_t Current, int64_t Total) {
 				ps->SetProgress(Current, Total);
 				return !ps->IsCancelled();
 			});