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

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https://hg.mozilla.org/integration/gaia-central/rev/625cb7376428
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19900 from jhford/depth1

Bug 1019243 - use a depth of 1 for shallow clones of Gaia

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https://hg.mozilla.org/integration/gaia-central/rev/3a3911118d82
Author: John Ford <john@johnford.info>
Desc: Bug 1019243 - use a depth of 1 for shallow clones of Gaia
Bumping manifests a=b2g-bump