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

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https://hg.mozilla.org/integration/gaia-central/rev/efdd545d3b03
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #19102 from dominickuo/bug-961980

Bug 961980 - [Settings] preview the tones in the sound region when adjusting the sliders, r=crh0716

========

https://hg.mozilla.org/integration/gaia-central/rev/0c01c5b7ee57
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Bug 961980 - [Settings] preview the tones in the sound region when adjusting the sliders

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "8a154c7caacaf05a3f1ef216dea6dc1efacc87cf", 
+    "revision": "efdd545d3b03ee8272cc0e7eae6b09a7c797d6f7", 
     "repo_path": "/integration/gaia-central"
 }