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

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https://hg.mozilla.org/integration/gaia-central/rev/d54340d6608a
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #16724 from bholley/fix_notification_spy

Bug 976935 - Use a stub rather than a spy for the Notification constructor. v2 r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/c170d5e645b7
Author: Bobby Holley <bobbyholley@gmail.com>
Desc: Bug 976935 - Use a stub rather than a spy for the Notification constructor. v2
Bumping manifests a=b2g-bump