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

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https://hg.mozilla.org/integration/gaia-central/rev/dc7f55f9fe4e
Author: Mason Chang <mason@masonchang.com>
Desc: Merge pull request #16764 from changm/bug976299

Bug 976299 - Settings that are translateX take an extra layer. r=:21

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https://hg.mozilla.org/integration/gaia-central/rev/54fb352311c5
Author: Mason Chang <mchang@mozilla.com>
Desc: Bug 976299 - Settings that are translateX take an extra layer
Bumping manifests a=b2g-bump