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

========

https://hg.mozilla.org/integration/gaia-central/rev/ac7418660457
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1022132 - Disable test_a11y_unlock_to_homescreen.py on TBPL

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "bc64c0e2f612d946b2b9d630940e953b27c439a4", 
+    "revision": "ac7418660457931afab3dc89f55b8fc8dafbd3df", 
     "repo_path": "/integration/gaia-central"
 }