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

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https://hg.mozilla.org/integration/gaia-central/rev/7840f22c9753
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #11906 from lightsofapollo/calendar-diable

disable intermittent failing test

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https://hg.mozilla.org/integration/gaia-central/rev/3dc9d8c5253c
Author: James Lal <james@lightsofapollo.com>
Desc: disable intermittent failing test

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https://hg.mozilla.org/integration/gaia-central/rev/a4e5688f0fe4
Author: b2gautomation <jonallengriffin@gmail.com>
Desc: Bug 907941 - gaia-ui-tests-pushbot (see bug)