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

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https://hg.mozilla.org/integration/gaia-central/rev/a9373a0a5aa0
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #22012 from rnowm/1041779

Bug 1041779 - [Messages][MMS] Download button styles are broken r=azasypkin

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https://hg.mozilla.org/integration/gaia-central/rev/710a36fc48ef
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 1041779 - [Messages][MMS] Download button styles are broken
Bumping manifests a=b2g-bump