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

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https://hg.mozilla.org/integration/gaia-central/rev/8dd238333b06
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #12262 from crdlc/bug-916936

Bug 916936 - Two dashes / underscores can be seen on each page of the homescreen

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https://hg.mozilla.org/integration/gaia-central/rev/7c4be8321ea4
Author: crdlc <crdlc@tid.es>
Desc: Bug 916936 - Two dashes / underscores can be seen on each page of the homescreen