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

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https://hg.mozilla.org/integration/gaia-central/rev/6c1fc5d47fed
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #13008 from zacc/bug_929468

Bug 929468 - Python fix the way tests use mock_contact.py

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https://hg.mozilla.org/integration/gaia-central/rev/6c5a910b6bb0
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 929468 - Python fix the way tests use mock_contact.py