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

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https://hg.mozilla.org/integration/gaia-central/rev/87ee678cab7e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #22497 from KevinGrandon/bug_1048543_homescreen_defer_save

Bug 1048543 - [Vertical Homescreen] Defer saving of grid until after initial render

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https://hg.mozilla.org/integration/gaia-central/rev/a91237bd689b
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1048543 - [Vertical Homescreen] Defer saving of grid until after initial render r=Cwiiis
Bumping manifests a=b2g-bump