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

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https://hg.mozilla.org/integration/gaia-central/rev/2dc86742fad9
Author: Malini Das <mdas@mozilla.com>
Desc: Bug 943008 - Enable pinning of marionette_client package in setup.py. r=dhunt

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https://hg.mozilla.org/integration/gaia-central/rev/87d721e7384b
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #14207 from Rik/dialer-error-944618

Bug 944618 - Remove a CSS error r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/a9e23b74cd5f
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 944618 - Remove a CSS error