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

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https://hg.mozilla.org/integration/gaia-central/rev/28c1686f93eb
Author: Yoshi Huang <allstars.chh@mozilla.com>
Desc: Merge pull request #18844 from svic/Bug_1002304

Bug 1002304 - Restore state of BT for incoming file transfers. r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/6711541b21b3
Author: Arno Puder <arno@puder.org>
Desc: Bug 1002304 - Restore state of BT for incoming file transfers. r=ehung

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "0b28cbe12ec78786664f17f05bc71a5260c36098", 
+    "revision": "28c1686f93eb870f7e683d9ada8426c2395ad53f", 
     "repo_path": "/integration/gaia-central"
 }