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

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https://hg.mozilla.org/integration/gaia-central/rev/24e7979d8127
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #19948 from jrburke/bug1018534-email-manifest-privileged

Bug 1018534 - [email] switch manifest type to privileged r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/3629fc09f539
Author: jrburke <jrburke@gmail.com>
Desc: Bug 1018534 - [email] switch manifest type to privileged
Bumping manifests a=b2g-bump