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

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https://hg.mozilla.org/integration/gaia-central/rev/d8c297cc7df5
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #23988 from etiennesegonzac/bug-1061324-followup-followup

Bug 1061324 Follow follow up - Making the whole task_manager_test suite ...

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https://hg.mozilla.org/integration/gaia-central/rev/d69437d6d9e8
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 1061324 Follow follow up - Making the whole task_manager_test suite use fakeTimers.
Bumping manifests a=b2g-bump