Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f1b21198eef3
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #12375 from gaye/bug-919724

Bug 919724 - Remove random, unused test-data/ directory from calendar

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https://hg.mozilla.org/integration/gaia-central/rev/961cfa3b3893
Author: Gareth Aye <gaye@mozilla.com>
Desc: Bug 919724 - Remove random, unused test-data/ directory from calendar

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https://hg.mozilla.org/integration/gaia-central/rev/4b2b83f329bf
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #12405 from gaye/bug-902124

Bug 902124 - Makefile should configure gaia-marionette

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https://hg.mozilla.org/integration/gaia-central/rev/67ff4ad08c3e
Author: Gareth Aye <gaye@mozilla.com>
Desc: Allow |make test-integration| to configure mocha reporter and npm registry