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

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https://hg.mozilla.org/integration/gaia-central/rev/68cb329d1719
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #12860 from bobsilverberg/br_timeout

Bug 925844 - Allow override of load timeout in Browser app object's go_to_url method, r=zac

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https://hg.mozilla.org/integration/gaia-central/rev/4c1786cd8d18
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 925844 - Allow override of load timeout in Browser app object's go_to_url method, r=zac