Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/6d2088f399b2
Author: Sherman Chen <shamen.chens@gmail.com>
Desc: Revert "Bug 1043708 - Music search bar should not have gradient background"

This reverts commit deaccef7409fd54e18c92c83383f39b7dca6f6dd.
Bumping manifests a=b2g-bump