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

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https://hg.mozilla.org/integration/gaia-central/rev/20e3f42ccb60
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #12635 from gasolin/issue-921327

Bug 921327 - [Flatfish][homescreen] show 6 icons in a row on tablet, r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/2a75bf172fcb
Author: gasolin <gasolin@gmail.com>
Desc: Bug 921327 - [Flatfish][homescreen] show 6 icons in a row on tablet