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

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https://hg.mozilla.org/integration/gaia-central/rev/f6556c09eb6c
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20841 from KevinGrandon/bug_839491_unrecoverable_app_install

Bug 839491 - Handle unrecoverable app installs from the homescreen/search/collections apps

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https://hg.mozilla.org/integration/gaia-central/rev/8067c03cac21
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 839491 - Handle unrecoverable app installs from the homescreen/search/collections apps r=kgrandon
Bumping manifests a=b2g-bump