[pitivi] Update GstTranscoder submodule

[Thibault Saunier <tsaunier src gnome org>]

commit 4ca2b5174a382ed5248908d914d705e5a6ca30f1
Author: Thibault Saunier <tsaunier gnome org>
Date:   Wed Jun 7 16:33:07 2017 -0400

    Update GstTranscoder submodule

 subprojects/gst-transcoder |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/subprojects/gst-transcoder b/subprojects/gst-transcoder
index a39c3e8..19292c6 160000
--- a/subprojects/gst-transcoder
+++ b/subprojects/gst-transcoder
@@ -1 +1 @@
-Subproject commit a39c3e8f8ae3b6f31f81d152ecc8f30e4838c09c
+Subproject commit 19292c6acb31484ae6b554cf972ffcfbbba0f12b