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

========

https://hg.mozilla.org/integration/gaia-central/rev/ff8c83f97fe8
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1016748 - Disable accessibility test due to travis perma-fail

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "7ee9a4eb33ad1ddd3d0808d08b40e12672dac993", 
+    "revision": "ff8c83f97fe8d6d5e21c0a1c5373083336c3be2a", 
     "repo_path": "/integration/gaia-central"
 }