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

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https://hg.mozilla.org/integration/gaia-central/rev/8d1fddd00cca
Author: Joan Leon <joan.leon@gmail.com>
Desc: Merge pull request #14257 from nucliweb/BB-validate

BB validate

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https://hg.mozilla.org/integration/gaia-central/rev/d8a9334d039d
Author: Joan Leon <joan.leon@gmail.com>
Desc: [BB] Fix to pass W3C Validator

Fix font-size on shared/style_unstable/lists.css on [data-type="list"]
aside.icon