Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/31e041c41372
Author: Julien Wajsberg <felash@gmail.com>
Desc: Revert "Merge pull request #12267 from pivanov/bug-908241"

This reverts commit 400d5fec2f099397575ded3ef8544150a9b472c5, reversing
changes made to a894561828a3a00ea54fe69fad26f0cadf6239fa.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "48274490bc2d1ae1bd45c3b2b74675605f018fae", 
+    "revision": "31e041c41372151066f27540c6a9e78fd4e8e987", 
     "repo_path": "/integration/gaia-central"
 }