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

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https://hg.mozilla.org/integration/gaia-central/rev/a991b9f51b4a
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #21574 from yurenju/camera-config

Bug 1036830 - build failed if camera-config.js in distribution directory... r=gduan

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https://hg.mozilla.org/integration/gaia-central/rev/a22047c24738
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 1036830 - build failed if camera-config.js in distribution directory doesn't exist r=gduan

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "2babb1f06da2d6a95d029940c75f7c753714eefb", 
+    "revision": "a991b9f51b4a6cb72e4de2cfbad6ab984eeb26db", 
     "repo_path": "/integration/gaia-central"
 }