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

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https://hg.mozilla.org/integration/gaia-central/rev/3c297dff9820
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #17210 from mikehenrty/bug-974734-notification-tests-reenable

Bug 974734 - Failing intermittent notifications test

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https://hg.mozilla.org/integration/gaia-central/rev/cf62c0fa7285
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 974734 - Failing intermittent notifications test
Bumping manifests a=b2g-bump