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

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https://hg.mozilla.org/integration/gaia-central/rev/4e20b480d24a
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 918743 - xfail test_cards_view_with_three_apps due to bug 915138. r=atriff