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

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https://hg.mozilla.org/integration/gaia-central/rev/427aac520587
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #13637 from wilsonpage/hud

Bug 933898 - [Camera] 1.3 Visual refresh of Heads Up Display

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https://hg.mozilla.org/integration/gaia-central/rev/3a8eb4028da2
Author: Wilson Page <wilsonpage@me.com>
Desc: Bug 933898 - [Camera] 1.3 Visual refresh of Heads Up Display (flash and front/rear toggle buttons)