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

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https://hg.mozilla.org/integration/gaia-central/rev/3737408a22be
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #23119 from qdot/938171-migrate-bookmarks

Bug 938171 - Browser Bookmark Migration to Homescreen in Gaia

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https://hg.mozilla.org/integration/gaia-central/rev/9f936a00d0d2
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 938171 - Browser Bookmark Migration to Homescreen in Gaia
Bumping manifests a=b2g-bump