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

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https://hg.mozilla.org/integration/gaia-central/rev/471fb1062bb7
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #14161 from arcturus/bug-944253

Bug 944253 - [Window Manager] Activity with window disposition is failing

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https://hg.mozilla.org/integration/gaia-central/rev/d38883d3d590
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Bug 944253 - [Window Manager] Activity with window disposition is failing