libmix: remove the work around for format change in video editor

BZ: 196532

This work around leads to one 1080i video clip no thumbnail displayed.
Remove it.

Change-Id: I26307bb31abfc5985d9feddeab046f5e8939f5c3
Signed-off-by: Tianmi Chen <tianmi.chen@intel.com>
Signed-off-by: Gu, Wangyi <wangyi.gu@intel.com>
1 file changed