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

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https://hg.mozilla.org/integration/gaia-central/rev/1679a2ea550c
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #14051 from jmcanterafonseca/fb_migration_datastore

Bug 924139 - Devise and implement a mechanism to migrate FB data between...

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https://hg.mozilla.org/integration/gaia-central/rev/b9552c87a716
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 924139 - Devise and implement a mechanism to migrate FB data between indexedDB and DataStore