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

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https://hg.mozilla.org/integration/gaia-central/rev/4ad25c0efbf4
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16089 from viorelaioia/bug_968737

Bug 968737 - Update test_unlock_to_camera_with_passcode to take a picture

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https://hg.mozilla.org/integration/gaia-central/rev/eac6dfb4062e
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 968737 - Update test_unlock_to_camera_with_passcode to take a picture

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "78a18bc9c0e6bd086110237d85b140124997b83b", 
+    "revision": "4ad25c0efbf4d29130c970d3b2a9f0fc074c177c", 
     "repo_path": "/integration/gaia-central"
 }