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

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https://hg.mozilla.org/integration/gaia-central/rev/f77159f52c38
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #13976 from aniruddha-adhikary/master

Bug 842592: Adding Bangla Input Method for B2G.
r=rudylu

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https://hg.mozilla.org/integration/gaia-central/rev/6f3ca118a255
Author: Aniruddha Adhikary <aniruddha@adhikary.net>
Desc: Bug 842592 - Adding Bangla Input Method for B2G