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

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https://hg.mozilla.org/integration/gaia-central/rev/a3fe7c4f3777
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #20184 from borjasalguero/mobileid_ui

Bug 1003330: Mobile identity UI. r=ferjm

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https://hg.mozilla.org/integration/gaia-central/rev/120c365fdf2a
Author: Borja Salguero <borja.bugzilla@gmail.com>
Desc: Bug 1003330: Mobile identity UI. r=ferjm
Bumping manifests a=b2g-bump