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

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https://hg.mozilla.org/integration/gaia-central/rev/3c421266eabd
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #15543 from Seinlin/Bug-961951

Bug 961951 - Fix can't display wifi network list. r=alive, arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/1a6c9e5f3b1e
Author: Kaizhen <kli@mozilla.com>
Desc: Bug 961951 - Fix can't display wifi network list.
Bumping manifests a=b2g-bump