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

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https://hg.mozilla.org/integration/gaia-central/rev/6930dd1da9f1
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #13138 from jmcanterafonseca/fb_datastore_final

Bug 923637 - Use DataStore instead of indexedDB in the fb_data.js module

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https://hg.mozilla.org/integration/gaia-central/rev/e6e229c2c9ee
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 923637 - Use DataStore instead of indexedDB in the fb_data.js module