[pitivi] Update gst-transcoder submodule

[Thibault Saunier <tsaunier src gnome org>]

commit a8de4ecd24f0770144a8063702b57cb5d82aedf9
Author: Thibault Saunier <thibault saunier osg samsung com>
Date:   Tue Jan 10 10:55:08 2017 -0300

    Update gst-transcoder submodule
    
    Several usefull feature have been added and... it adds interesting EncodingTargets
    
    Differential Revision: https://phabricator.freedesktop.org/D1605

 subprojects/gst-transcoder |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/subprojects/gst-transcoder b/subprojects/gst-transcoder
index 6ff7f83..6d4362a 160000
--- a/subprojects/gst-transcoder
+++ b/subprojects/gst-transcoder
@@ -1 +1 @@
-Subproject commit 6ff7f832f29e8a8c89673c6bac4e3a1b27a28041
+Subproject commit 6d4362a5bc5043e83caf260d20e3ff4d97597a1d