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

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https://hg.mozilla.org/integration/gaia-central/rev/871c9c2aa082
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Merge pull request #12134 from fabi1cazenave/macAddress-bug895739

Bug 895739 - [Wi-Fi] MAC address is always displayed as "not available", r=Arthur

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https://hg.mozilla.org/integration/gaia-central/rev/fd3cf07a9c84
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Bug 895739 - [Wi-Fi] MAC address is always displayed as "not available"