[pitivi] elements: Do not connect transition '_childAddedCb' twice

[Alexandru Băluț <alexbalut src gnome org>]

commit 4342147230fca57398eca0b168b5570ab59d7523
Author: Thibault Saunier <tsaunier gnome org>
Date:   Mon Dec 21 09:54:21 2015 +0100

    elements: Do not connect transition '_childAddedCb' twice
    
    Differential Revision: https://phabricator.freedesktop.org/D596

 pitivi/timeline/elements.py |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/timeline/elements.py b/pitivi/timeline/elements.py
index 9f731b1..16199ae 100644
--- a/pitivi/timeline/elements.py
+++ b/pitivi/timeline/elements.py
@@ -973,8 +973,6 @@ class TransitionClip(Clip):
 
         self.get_style_context().add_class("TransitionClip")
 
-        self.bClip.connect("child-added", self._childAddedCb)
-
         # In the case of TransitionClips, we are the only container
         self._addTrimHandles()