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

========

https://hg.mozilla.org/integration/gaia-central/rev/18667a9b93ea
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 935442 - [System] 1 unit tests failure with the latest firefox builds r=alive

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "8b613bca552487199ee0f9ecebe43fa854387a88", 
+    "revision": "18667a9b93eaccd93d7f1fa681e4e32aa63405a3", 
     "repo_path": "/integration/gaia-central"
 }