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

========

https://hg.mozilla.org/integration/gaia-central/rev/bf28369024d0
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #15863 from daleharvey/966137

Bug 966137 - Ensure we only attempt one datastore write operation at a time. r=kgrandon

========

https://hg.mozilla.org/integration/gaia-central/rev/a34c5f3eee19
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 966137 - Ensure we only attempt one datastore write operation at a time. r=kgrandon
Bumping manifests a=b2g-bump