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

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https://hg.mozilla.org/integration/gaia-central/rev/54bc4e9f023e
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Merge pull request #14007 from EverythingMe/924468-collections-organize

Bug 924468 - Adding re-organizing functionality to edit mode in Collecti...

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https://hg.mozilla.org/integration/gaia-central/rev/61f59797f2d6
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Bug 924468 - Adding re-organizing functionality to edit mode in Collections r=[crdlc, ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/4cc612abef6c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #13849 from JohanLorenzo/test-flick-calendar-through-months

Bug 937085 - Write test to flick calendar through months

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https://hg.mozilla.org/integration/gaia-central/rev/b743586d0de9
Author: Johan LORENZO <johan.lorenzo@gmail.com>
Desc: Bug 937085 - Write test to flick calendar through months

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "c4922d919973127ccde39105deec5c87933e3b47", 
+    "revision": "54bc4e9f023e4bdf1454504e92017bd8f008d72e", 
     "repo_path": "/integration/gaia-central"
 }