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

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https://hg.mozilla.org/integration/gaia-central/rev/9c89bc252dca
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #13276 from gasolin/issue-919927

Bug 919927 - [Permission] use permissions instead of permission/option/o...,r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/81325984348c
Author: gasolin <gasolin@gmail.com>
Desc: Bug 919927 - [Permission] use permissions instead of permission/option/options