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

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https://hg.mozilla.org/integration/gaia-central/rev/dbe078ff4f76
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #13021 from viorelaioia/bug-929799

Bug 929799 - tbpl-manifest.ini is out of date with what tests can be ena...

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https://hg.mozilla.org/integration/gaia-central/rev/078f43f5833a
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 929799 - tbpl-manifest.ini is out of date with what tests can be enabled & removed