Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/3bfa2705ae29
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 917196 - When short tones are enabled make audible tones short too r=etienne

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "3e61ebc75d30f2422bc69a50b06689d9262020f9", 
+    "revision": "3bfa2705ae298359daa7036a8f77e33a2e19f7b6", 
     "repo_path": "/integration/gaia-central"
 }