Bumping gaia.json for 2 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/c4c9bc243d45
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #12823 from teodosia/update-activities

Bug 926460 - Update Activities system region locators

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https://hg.mozilla.org/integration/gaia-1_2/rev/52343a645bcb
Author: Teodosia Pop <teodosia.pop@gmail.com>
Desc: Bug 926460 - Update Activities system region locators