Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/3fd45e3c7d86
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1021496 - Follow-up, add grid_icon_renderer to example r=me

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https://hg.mozilla.org/integration/gaia-2_0/rev/82ad5a0ddd28
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1021496 - [Vertical] Implement bookmark app icon design from Classic Homescreen r=crdlc

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https://hg.mozilla.org/integration/gaia-2_0/rev/f5962a1bd01d
Author: crdlc <crdlc@tid.es>
Desc: Bug 1025855 - [Vertical Homescreen] Wrong box shadow for bookmarks in edit mode

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https://hg.mozilla.org/integration/gaia-2_0/rev/0ac8aeb54bd4
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Bug 1025844 - [Collections] Missing Default Icon and faster Background load
Bumping manifests a=b2g-bump