Commit 8a56a7de (camerabin2: preview:
Appsink doesn't need to sync) add a line that set the "sync" property on
the appsink. However, the author seems to forget that there's another
property setting on appsink a few lines below.
It's very likely that the added line is required because the original
line doesn't take effect (maybe because it's too late). But for whatever
reason, the original line is now redundant. So, I remove it in this