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

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https://hg.mozilla.org/integration/gaia-central/rev/0c92e7791796
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #15599 from jmcanterafonseca/fix_fb_index_write

Bug 950881 In the Facebook datastore simplify indexing by removing the m...

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https://hg.mozilla.org/integration/gaia-central/rev/5f2d19440ad0
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 950881 In the Facebook datastore simplify indexing by removing the mapping uids --> dsids
Bumping manifests a=b2g-bump