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

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https://hg.mozilla.org/integration/gaia-2_0/rev/62250d4ae59f
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #21561 from alivedise/bugzilla/1027401_v2.0/child-window-event-handler

Bug 1027401 - Change child event mechanism, r=etienne

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https://hg.mozilla.org/integration/gaia-2_0/rev/2f583c53f421
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1027401 - Change child event mechanism
Bumping manifests a=b2g-bump