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

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https://hg.mozilla.org/integration/gaia-central/rev/c0b6498daf59
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #11218 from yurenju/898256

bug 898256 - Use new 1.5x assets from UX for shared style r=basiclines

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https://hg.mozilla.org/integration/gaia-central/rev/e4c746dd723e
Author: Yuren Ju <yurenju@gmail.com>
Desc: bug 898256 - Use new 1.5x assets from UX for shared style