Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e796d45a31d0
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #16541 from 6a68/bug-974108-iac-race-condition

Bug 974108 - Race condition in FxAccountsIACHelper

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https://hg.mozilla.org/integration/gaia-central/rev/7295778e446b
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 974108 - Race condition in FxAccountsIACHelper

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https://hg.mozilla.org/integration/gaia-central/rev/3ffc04e5ef9b
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 983171 - [Settings] Disable intermittent failing tests
Bumping manifests a=b2g-bump