Bumping gaia.json for 1 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/e21c95b7c0ad
Author: b2gautomation <jonallengriffin@gmail.com>
Desc: Update gaia-ui-tests.json; Merge pull request #1367 from davehunt/bug916072

Bug 916072 - Update cleanup to reflect change of persistent storage path