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

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https://hg.mozilla.org/integration/gaia-central/rev/0274bf4c7d95
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #19671 from azasypkin/bug-963013-visual-styles

Bug 963013 - [Messages][Refresh] Update bubbles style and layout of the thread. Updated message bubble styles. r=schung

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https://hg.mozilla.org/integration/gaia-central/rev/f26f397d3111
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 963013 - [Messages][Refresh] Update bubbles style and layout of the thread. Updated message bubble styles. r=schung
Bumping manifests a=b2g-bump