Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f31df80b4f3f
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #21879 from gaye/bump-chai-to-1.9.1

Upgrade chai to 1.9.1 to downstream assert.notInclude

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https://hg.mozilla.org/integration/gaia-central/rev/0af98e7f74f1
Author: gaye <gaye@mozilla.com>
Desc: Upgrade chai to 1.9.1 to downstream assert.notInclude

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https://hg.mozilla.org/integration/gaia-central/rev/967625a4fa81
Author: James Graham <james@hoppipolla.co.uk>
Desc: Bug 1040045 - Move code for waiting for the homescreen in gaiatest into its own method. r=dhunt
Bumping manifests a=b2g-bump