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

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https://hg.mozilla.org/integration/gaia-central/rev/20b7d51bd03d
Author: Dale  Harvey <dale@arandomurl.com>
Desc: Merge pull request #10702 from benfrancis/796565

Bug 796565 - Share URL of web page - browser part. r=daleharvey

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https://hg.mozilla.org/integration/gaia-central/rev/72758617318e
Author: Ben Francis <ben@tola.me.uk>
Desc: Bug 796565 - Share URL of web page - browser part