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

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https://hg.mozilla.org/integration/gaia-central/rev/4c4ffe7f2c16
Author: Dave Hylands <dhylands@gmail.com>
Desc: Merge pull request #24236 from dhylands/bug-1059484-enable-sdcard1

Bug 1059484 - Enable sharing on the external storage card called sdcard1...

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https://hg.mozilla.org/integration/gaia-central/rev/64a7678f2e6b
Author: Dave Hylands <dhylands@gmail.com>
Desc: Bug 1059484 - Enable sharing on the external storage card called sdcard1. r=arthur.chen

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "9ded69d21786aaf37fa95cc3d4104ffc493fa473", 
+    "revision": "4c4ffe7f2c16edb4b612b8e81a3785c8384a33ad", 
     "repo_path": "/integration/gaia-central"
 }