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

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https://hg.mozilla.org/integration/gaia-central/rev/81652ec33eb5
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #25892 from davidflanagan/revert-bug1079519

Revert "Merge pull request #25627 from russnicoletti/bug-1079519"

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https://hg.mozilla.org/integration/gaia-central/rev/78887f9281c0
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Revert "Merge pull request #25627 from russnicoletti/bug-1079519"

This reverts commit 7bac3bc2379453196a95117e72670009a4d856e0, reversing
changes made to 1f621c11282161cc47870ab2c8d046103270dc71.

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "d29b9e448c52882a52ce03873081d43422715db3", 
+    "revision": "81652ec33eb529abb3d4175eb6f8b93ddf673d50", 
     "repo_path": "/integration/gaia-central"
 }