Bumping gaia.json for 2 gaia-central revision(s)

========

https://hg.mozilla.org/integration/gaia-central/rev/dd3c70c2565f
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #12107 from crh0716/914152

Bug 914152 - Add a selector for choosing DTMF tones r=evelyn

========

https://hg.mozilla.org/integration/gaia-central/rev/ae540b5323bc
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 914152 - Add a selector for choosing DTMF tones

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "ec77324395be1969cb408f863b5715dfa068321d", 
+    "revision": "dd3c70c2565f5ba5b4b643160b3e3e7f9ff7d87b", 
     "repo_path": "/integration/gaia-central"
 }