Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/9c2535d91b97
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1131773 - merge pull request #29258 from crh0716:1131773 to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/f78b7c7c27fa
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 1131773 - Add an addon-details panel to the Settings app
- Include system apps, homescreens, etc. in the list of target apps
- Figure out whether we need to reboot or restart apps after disabling an addon
- Show a toast to remind user to restart or reboot when disabling an add-on
- Reflect the addon enabled state changes even they are made outside settings app

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https://hg.mozilla.org/integration/gaia-central/rev/293f8a19d37c
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1153107 - merge pull request #29449 from dwi2:bug1153107 to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/ddf41c174298
Author: Tzu-Lin Huang <tzhuang@mozilla.com>
Desc: Bug 1153107 - fix 'folder.cardsInFolder is undefined' error and move folder-related logic back to folder.js

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "ca692311bddbd54b2fc7a2d507a68b2d0dd487c2", 
+        "git_revision": "749b6eb12c103f4119f1f85c72dbe7791684d8dc", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "c44e5ee53a98f7864341c8cca6d14b05f9714b19", 
+    "revision": "9c2535d91b978173334987211b04d4962c3042af", 
     "repo_path": "integration/gaia-central"
 }