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

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https://hg.mozilla.org/integration/gaia-central/rev/a4ef800576e5
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #14704 from KevinGrandon/bug_826274_annoying_sound

Bug 826274 - Disabled lock screen sound still plays r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/221a6c457f11
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 826274 - Disabled lock screen sound still plays

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "79e25f81e1e868ea9903eca5dd7452f2c778c7ce", 
+    "revision": "a4ef800576e55c9fb982bede3d0a7bbcea985f1c", 
     "repo_path": "/integration/gaia-central"
 }