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

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https://hg.mozilla.org/integration/gaia-central/rev/ced20196ea94
Author: Fabien Cazenave <fabien@mozilla.com>
Desc: Merge pull request #16768 from anefzaoui/RtlDeveloperHUD

Bug 978581 - (gaia-rtl) Developer HUD icons misplaced, r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/a5fae501e76b
Author: anefzaoui <nefzaoui.ahmed@hotmail.com>
Desc: Bug 978581 - (gaia-rtl) Developer HUD icons misplaced
Bumping manifests a=b2g-bump