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

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https://hg.mozilla.org/integration/gaia-central/rev/7623d9ee18c3
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #16758 from KevinGrandon/bug_978433_disable_failing_test

Bug 978433 - Disable intermittent failing unit test

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https://hg.mozilla.org/integration/gaia-central/rev/64cd7852973f
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 978433 - Disable intermittent failing unit test
Bumping manifests a=b2g-bump