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

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https://hg.mozilla.org/integration/gaia-central/rev/4bbc9f71b0e3
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #13134 from rnowm/931693

Bug 931693 - Confirm [BB] - Fix console warning due to flex property

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https://hg.mozilla.org/integration/gaia-central/rev/81d3ebe3d0a0
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 931693 - Confirm [BB] - Fix console warning due to flex property

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "4e0897d8651b9833b80793246df03ec885fb463d", 
+    "revision": "4bbc9f71b0e3b607f53187c4721b2d9086f1d337", 
     "repo_path": "/integration/gaia-central"
 }