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

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https://hg.mozilla.org/integration/gaia-central/rev/9bb13b4fca4d
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #23848 from daleharvey/1053261

Bug 1053261 - Add customisable preloaded top sites.

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https://hg.mozilla.org/integration/gaia-central/rev/952e0c5ac8cd
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 1053261 - Add customisable preloaded top sites. r=kgrandon
Bumping manifests a=b2g-bump