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

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https://hg.mozilla.org/integration/gaia-central/rev/c1b21713ac2e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #15909 from KevinGrandon/bug_966975_task_manager_transition

Bug 966975 - Task manager cards jump when entering from rocketbar r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/0f72fd08a7e8
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 966975 - Task manager cards jump when entering from rocketbar
Bumping manifests a=b2g-bump