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

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https://hg.mozilla.org/integration/gaia-central/rev/dce78731174c
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #14413 from crdlc/bug-946728

Bug 946728 - DragDrop unit tests are very slow and sometimes fires timeo...

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https://hg.mozilla.org/integration/gaia-central/rev/e38729b963fe
Author: crdlc <crdlc@tid.es>
Desc: Bug 946728 - DragDrop unit tests are very slow and sometimes fires timeouts