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

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https://hg.mozilla.org/integration/gaia-central/rev/d088194ed875
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #12751 from bobsilverberg/b2gstart

Bug 924918 - Extend the time we are waiting for b2g to start, to address problems running tests on devices, r=zac

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https://hg.mozilla.org/integration/gaia-central/rev/bd691d36a21d
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 924918 - Extend the time we are waiting for b2g to start, to address problems running tests on devices, r=zac