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

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https://hg.mozilla.org/integration/gaia-central/rev/3ea8f692956a
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #19703 from yor-mozilla-com/gaia-header-keyboard

Bug 1015295 - [Keyboard] Update to use gaia-header.
r=rudylu.

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https://hg.mozilla.org/integration/gaia-central/rev/7549c753503d
Author: Yan Or <yor@mozilla.com>
Desc: Bug 1015295 - [Keyboard] Update to use gaia-header
Bumping manifests a=b2g-bump