Bumping gaia.json for 4 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/f71d436bdcdd
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #11371 from LeeChSien/Bug_901862

Bug 901862 - [Test][System] Unit test for Utility Tray, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/ab8edeaba303
Author: Jason Lee <chsien@gmail.com>
Desc: Bug 901862 - [Test][System] Unit test for Utility Tray

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https://hg.mozilla.org/integration/gaia-central/rev/d644f1f71aea
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #11280 from huchengtw-moz/camera/Bug_897356_2_camera_cannot_work_when_plug_out_usb

Bug 897356 - [Buri][Contacts][Camera]The camera can't work when plug out...

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https://hg.mozilla.org/integration/gaia-central/rev/bd7b5f02bbb9
Author: John Hu <johu@mozilla.com>
Desc: Bug 897356 - [Buri][Contacts][Camera]The camera can't work when plug out USB

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "fd0d9515e6af1d7fdf8d40133d4706eb6e4b5938", 
+    "revision": "f71d436bdcddb4078b424bc6efbe661cbbdef83d", 
     "repo_path": "/integration/gaia-central"
 }