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

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https://hg.mozilla.org/integration/gaia-central/rev/2cadc5d69c72
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Merge pull request #14752 from gregorwagner/back

Travis bustage fix.

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https://hg.mozilla.org/integration/gaia-central/rev/9005e1961498
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Travis bustage fix