Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/72ac9b19f59a
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #12841 from lightsofapollo/break-the-world

update marionette client

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https://hg.mozilla.org/integration/gaia-central/rev/d4c81d84d737
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 927475 - update marionette client