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

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https://hg.mozilla.org/integration/gaia-central/rev/2172a8ae2e64
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #12139 from arasbm/bug-909373-openaudio-activity-save-robustness

bug-909373-[Music] open activity saving feature robustness, r=@dominickuo

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https://hg.mozilla.org/integration/gaia-central/rev/176261f18241
Author: Aras Balali Moghaddam <arasbm@gmail.com>
Desc: bug-909373-[Music] open activity saving feature robustness