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

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https://hg.mozilla.org/integration/gaia-central/rev/29680b72e627
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #12169 from hotzenklotz/915661_marionette_gallery

Bug 915661 - [Gallery] Add Marionette tests

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https://hg.mozilla.org/integration/gaia-central/rev/eb5797c5fe06
Author: Tom Herold <therold@mozilla.com>
Desc: Bug 915661 - [Gallery] Add Marionette tests

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "7ff699982f868613e4855c960c406313dd8af6f1", 
+    "revision": "29680b72e6277e56bf883c25818826a3fde5edb9", 
     "repo_path": "/integration/gaia-central"
 }