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

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https://hg.mozilla.org/integration/gaia-central/rev/f086def2b403
Author: Fabien Cazenave <fabien@mozilla.com>
Desc: Merge pull request #15154 from anefzaoui/BB-HeadersRtlFix

Bug 883673 - [BB][Headers] RTL is messed up, r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/436e5d953ce5
Author: Ahmed Nefzaoui <nefzaoui.ahmed@hotmail.com>
Desc: Bug 883673 - [BB][Headers] RTL is messed up, r=kaze