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

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https://hg.mozilla.org/integration/gaia-central/rev/207f9be38148
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #13869 from zacc/bug_939792

Bug 939792 - Remove get_active_frame from keyboard app object and other ...

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https://hg.mozilla.org/integration/gaia-central/rev/3fb541db9e77
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 939792 - Remove get_active_frame from keyboard app object and other app objects, make keyboard methods fall back to displayed_frame