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

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https://hg.mozilla.org/integration/gaia-central/rev/7978606c6bf0
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #14422 from etiennesegonzac/bug-943236-edge-gesture-logic

Bug 943236 - Move the current app to the top of the stack if the app opens a window. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/98baec1ddb4e
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 943236 - Move the current app to the top of the stack if the app
opens a window.