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

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https://hg.mozilla.org/integration/gaia-central/rev/837a95ee7a5d
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #14565 from crdlc/bug-924843

Bug 924843 - Icons on grid do not re-arrange automatically when dragging...

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https://hg.mozilla.org/integration/gaia-central/rev/18421b9ecd89
Author: crdlc <crdlc@tid.es>
Desc: Bug 924843 - Icons on grid do not re-arrange automatically when dragging over collections