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

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https://hg.mozilla.org/integration/gaia-central/rev/2761bef23995
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 969280 - disabling all navigation bar tests in dialer for tbpl bustage
Bumping manifests a=b2g-bump