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

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https://hg.mozilla.org/integration/gaia-central/rev/d637da82bcf3
Author: Andrew Sutherland <asutherland@asutherland.org>
Desc: Merge pull request #20488 from asutherland/email-ios-images

Bug 851963 - [email] iOS mail client attached images may be treated as embedded images that cannot be viewed because there is no referencing text/html part. r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/508f62788dd9
Author: Andrew Sutherland <asutherland@asutherland.org>
Desc: Bug 851963 - [email] iOS mail client attached images may be treated as embedded images that cannot be viewed because there is no referencing text/html part. r=asuth

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/309
Bumping manifests a=b2g-bump