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

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https://hg.mozilla.org/integration/gaia-central/rev/a4c7ffc5619e
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #15391 from jrburke/bug960290-email-trigger-offscreen

Bug 960290 - email: possible to trigger off-screen compose button r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/4bccb09ddfb7
Author: jrburke <jrburke@gmail.com>
Desc: Bug 960290 - email: possible to trigger off-screen compose button

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "e1445ee1e07006e74ba0cf7b3c50080808324f44", 
+    "revision": "a4c7ffc5619edd7e87fd763bd8a32291f4d394ac", 
     "repo_path": "/integration/gaia-central"
 }