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

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https://hg.mozilla.org/integration/gaia-central/rev/53a930e0a23a
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #14731 from qdot/950876-support-contacts-test

Bug 950876: Fix Support Contacts unit test to use Support Contacts customizer

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https://hg.mozilla.org/integration/gaia-central/rev/a9e2e0d1cbc5
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 950876: Fix Support Contacts unit test to use Support Contacts customizer