Bumping gaia.json for 3 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/3c94d18366dc
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #12206 from qdot/915920

Bug 915920 - APN values should only be updated once per phone boot

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https://hg.mozilla.org/integration/gaia-central/rev/7a1153fc85a6
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 915920 - Fix operator variant MCC and rebuild apn.json

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https://hg.mozilla.org/integration/gaia-central/rev/6ac1e028b438
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 915920 - ensure APN settings only get applied once per boot.