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

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https://hg.mozilla.org/integration/gaia-central/rev/347e465a2a9b
Author: Ghislain 'Aus' Lacroix <aus@noiseport.org>
Desc: Merge pull request #17303 from nullaus/bug982006

bug 982006

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https://hg.mozilla.org/integration/gaia-central/rev/b2ea4034c90f
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 982006

* Use new error nsresult values in download notifications.
* Update mock_download_ui.js based on addition of 'ERRORS' to DownloadUI.
* added tests for new Downloads API errors in download notifications test
* added new tests for modal dialog changes in app modal dialog test
* AppModalDialog will ignore titles that contain the application URL or origin and instead
  use the app name if it is available. If not, it will simply use an empty string.

r=alive, crdlc
Bumping manifests a=b2g-bump