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

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https://hg.mozilla.org/integration/gaia-central/rev/4839476d648c
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #10925 from masap/20130711

Bug 892434 - [WiFi] Fix Showing gone network r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/18fb5d823e8b
Author: masap <masashi.honma@gmail.com>
Desc: Bug 892434 - [WiFi] Fix Showing gone network