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

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https://hg.mozilla.org/integration/gaia-central/rev/de5bdd5f103b
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #15313 from gaye/clean-up-create-event-tests

Bug 959710 - Use marionette-plugin-forms to simplify Calendar#createEvent r=millermedeiros

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https://hg.mozilla.org/integration/gaia-central/rev/376d25f597bd
Author: Gareth Aye <gaye@mozilla.com>
Desc: Bug 959710 - Use marionette-plugin-forms to simplify Calendar#createEvent