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

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https://hg.mozilla.org/integration/gaia-central/rev/f785af917ac4
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1139236 - merge pull request #28614 from KevinGrandon:bug_1139236_move_sheets_apps to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/28f1b229b339
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1139236 - Move sheet test apps into system fixtures folder r=etienne

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "f3b486c15bf09a4ddf0a274ad64036907aff0320", 
+        "git_revision": "72af4b9dcac6d32231a5772540fb9734d1bb9f6c", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "802e98f4939c397a2cd7ef1b61b67513c494a3bb", 
+    "revision": "f785af917ac461d436d0da30505d3a918bcba570", 
     "repo_path": "integration/gaia-central"
 }