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

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https://hg.mozilla.org/integration/gaia-central/rev/f57e008fc1f0
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #13563 from dmarcos/bug931125

Bug 931125 - [Gallery] [Camera] We have to take into account the screen ...

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https://hg.mozilla.org/integration/gaia-central/rev/54c8c9978353
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Bug 931125 - [Gallery] [Camera] We have to take into account the screen pixel ratio when checking if the thumbnail fills the screen