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

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https://hg.mozilla.org/integration/gaia-central/rev/cf79923c9bf7
Author: Ghislain 'Aus' Lacroix <aus@noiseport.org>
Desc: Merge pull request #21931 from nullaus/bug1038167

bug 1038167 - Remove 80x80, 256x256. Add 84x84. Update System to correct...

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https://hg.mozilla.org/integration/gaia-central/rev/d4f30b69f139
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 1038167 - Remove 80x80, 256x256. Add 84x84. Update System to correct icons. r=timdream
Bumping manifests a=b2g-bump