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

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https://hg.mozilla.org/integration/gaia-central/rev/66779b0cc46a
Author: dwi2 <dwi2@dwi2.com>
Desc: Merge pull request #16021 from dwi2/bug952610

Bug 952610 - Bookmark installation test failure

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https://hg.mozilla.org/integration/gaia-central/rev/3cfd9dff1e9b
Author: tzhuang <tzhuang@mozilla.com>
Desc: Bug 952610 - Re-enable marionette js test of homescreen
Bumping manifests a=b2g-bump