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

========

https://hg.mozilla.org/integration/gaia-central/rev/470c81220a0a
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #13052 from denehs/bug928821

Bug 928821 - B2G MMS: put deliveryStatus[] into a more generic structure...

========

https://hg.mozilla.org/integration/gaia-central/rev/342bbe4dd3c4
Author: Shao Hang Kao <denehs@gmail.com>
Desc: Bug 928821 - B2G MMS: put deliveryStatus[] into a more generic structure MmsDeliveryInfo[]

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "9390a2bb89156badf31def75d36ffc76da30d5ad", 
+    "revision": "470c81220a0ac2ce33597e12c2300a61590d133d", 
     "repo_path": "/integration/gaia-central"
 }