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

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https://hg.mozilla.org/integration/gaia-central/rev/9f9909a9fac7
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #16473 from yurenju/twice

Bug 974376 - Marionnette JS tests are reported twice on Travis and locally. r=@evanxd

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https://hg.mozilla.org/integration/gaia-central/rev/9728b78e745f
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 974376 - Marionnette JS tests are reported twice on Travis and locally.
Bumping manifests a=b2g-bump