Remove svn export hook.

Hook was incorrectly overwriting directory whenever
gclient runhooks was issued.
Review URL: http://webrtc-codereview.appspot.com/194001

git-svn-id: http://libyuv.googlecode.com/svn/trunk@9 16f28f9a-4ce2-e073-06de-1de4eb20be90

DEPS

@@ -18,10 +18,6 @@ deps = {
 
 
 hooks = [
-  {
-    "pattern": ".",
-    "action": ["svn", "export", Var("libyuv_trunk"), "--force"],
-  },
   # A change to a .gyp, .gypi, or to GYP itself should run the generator.
   {
     "pattern": ".",