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

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https://hg.mozilla.org/integration/gaia-central/rev/bbb67241e1bc
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #12015 from gasolin/issue-911679

Bug 911679 - add init screen logo for large device, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/d7675d542643
Author: gasolin <gasolin@gmail.com>
Desc: Bug 911679 - [system] add init screen logo for large device