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

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https://hg.mozilla.org/integration/gaia-central/rev/4b3901a5adee
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #23656 from qdot/1061804-browser-opvar-followup

Bug 1061804 - Browser OpVar Customization Fixes

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https://hg.mozilla.org/integration/gaia-central/rev/d1ecfd6d9cc1
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 1061804 - Browser OpVar Customization Fixes

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "2a85bee097d05f8d5f74098f127c6f4b7086eb29", 
+    "revision": "4b3901a5adeeeeaba92b61c35ac531dfb8936bb0", 
     "repo_path": "/integration/gaia-central"
 }