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

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https://hg.mozilla.org/integration/gaia-central/rev/ad91f0092cb2
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #13255 from timdream/keyboard-perm-safenet

Bug 915570 - Rename 'keyboard' permission and role to 'input', r=rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/a9a800b1f112
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 915570 - Rename 'keyboard' permission and role to 'input'

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "b7dce66e2f502a25b4dd1abaf03ad719316f5bef", 
+    "revision": "ad91f0092cb25284d4ed4fa88576a89e7e15c6bd", 
     "repo_path": "/integration/gaia-central"
 }