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

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https://hg.mozilla.org/integration/gaia-central/rev/b5d66bc31278
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #12281 from eeejay/bug-916231

Bug 916231 - Add screen reader toggle to developer options. r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/706499ea0abd
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 916231 - Add screen reader toggle to developer options.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "2abf97674c6a9801e8dbf1d85bdd2c6178c90a19", 
+    "revision": "b5d66bc312782d4214c878a0cb74f8c96f6288d5", 
     "repo_path": "/integration/gaia-central"
 }