Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/9497c73bc475
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Revert "Merge pull request #17860 from mcav/alarm-volume-2"

This reverts commit 6e6cf2c0e135542da4aacce710cd534794b9627e, reversing
changes made to c648699d636414c50cf29ea3173058a0c78a855f.

Conflicts:
	apps/clock/js/panels/timer/main.js
Bumping manifests a=b2g-bump