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

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https://hg.mozilla.org/integration/gaia-central/rev/f828879a8072
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #21003 from jimporter/email-as-download-body-failure

Bug 1009422 - [email/Activesync/hotmail] Apparent change in server behav...

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https://hg.mozilla.org/integration/gaia-central/rev/a452727cbd3a
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1009422 - [email/Activesync/hotmail] Apparent change in server behaviour resulting in regression in downloadBodies due to missing body payload; results in operation hang, breaking all operations in the folder
Bumping manifests a=b2g-bump