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

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https://hg.mozilla.org/integration/gaia-central/rev/6299cd16b333
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #15533 from willyaranda/961718

Bug 961718. enableUSBStorage1 is shared in two different places. r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/061d3dc2861a
Author: Guillermo Lopez <willyaranda@mozilla-hispano.org>
Desc: Bug 961718. enableUSBStorage1 is shared in two different places
Bumping manifests a=b2g-bump