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

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https://hg.mozilla.org/integration/gaia-central/rev/feac2c7f4eb4
Author: crdlc <crdlc@tid.es>
Desc: [B2G][2.0][VerticalHomescreen] The icons of downloaded apps are not displayed r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/386c5d786fe3
Author: crdlc <crdlc@tid.es>
Desc: Bug 1015505 - [B2G][2.0][VerticalHomescreen] When an app is downloaded from the 4-column layout, the icon is displayed in a smaller size r=kgrandon
Bumping manifests a=b2g-bump