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

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https://hg.mozilla.org/integration/gaia-central/rev/bb4a52c0438c
Author: Fernando Jiménez Moreno <ferjmoreno@gmail.com>
Desc: Merge pull request #11229 from ferjm/paymenteventlistener

Bug 899153 - TypeError: this.removeEventListener is not a function in pa...

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https://hg.mozilla.org/integration/gaia-central/rev/dd1834c7454a
Author: Fernando Jiménez <ferjmoreno@gmail.com>
Desc: Bug 899153 - TypeError: this.removeEventListener is not a function in payment.js. r=vingtetun

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "e40805193a375e757b0d59f10c7ceec67e74c3c3", 
+    "revision": "bb4a52c0438c109ecea03ef36e31aa076dabecb5", 
     "repo_path": "/integration/gaia-central"
 }