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

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https://hg.mozilla.org/integration/gaia-central/rev/a2f40dcb6d96
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #20089 from yzen/bug-1021137

Bug 1021137 - added missing aria attributes the the lockscreen's passcod...

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https://hg.mozilla.org/integration/gaia-central/rev/df230835fcec
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1021137 - added missing aria attributes the the lockscreen's passcode panel and media container. r=alive

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "ece1e6123344703645ef17c9b85d3af3a24134ce", 
+    "revision": "a2f40dcb6d96592d223e13df4fc4b7b48a8b1ee0", 
     "repo_path": "/integration/gaia-central"
 }