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

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https://hg.mozilla.org/integration/gaia-central/rev/e9a78936b14d
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #14684 from cctuan/905495

Bug 905495 - unit test infrastructure for gaia build system

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https://hg.mozilla.org/integration/gaia-central/rev/420122ef7a3b
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 905495 - unit test infrastructure for gaia build system
merge b2g-inbound to mozilla-central