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

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https://hg.mozilla.org/integration/gaia-central/rev/28ee3fb643b9
Author: Jan Keromnes <janx@linux.com>
Desc: Merge pull request #17450 from jankeromnes/svgbadge

Bug 986504 - Use SVG badge for travis build status in README.md r=me

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https://hg.mozilla.org/integration/gaia-central/rev/d1ff8fd3a8b4
Author: Jan Keromnes <janx@linux.com>
Desc: Bug 986504 - Use SVG badge for travis build status in README.md
Bumping manifests a=b2g-bump