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

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https://hg.mozilla.org/integration/gaia-central/rev/4a3edbca9b79
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #18926 from dominickuo/bug-998906

Bug 998906 - [Music] display the correct overlay after the enumeration in ListView, r=jimporter

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https://hg.mozilla.org/integration/gaia-central/rev/fc62976ca79f
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Bug 998906 - [Music] display the correct overlay after the enumeration in ListView
Bumping manifests a=b2g-bump