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

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https://hg.mozilla.org/integration/gaia-central/rev/e104df5519d2
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #14404 from rnowm/sticky-headers-SMS

Bug 946693 - Fix sticky headers in [SMS] app

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https://hg.mozilla.org/integration/gaia-central/rev/881d357fe8d3
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 946693 - Fix sticky headers in [SMS] app