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

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https://hg.mozilla.org/integration/gaia-1_4/rev/71cca8a58ca6
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 988760 - Workaround for glitchy sound when playing the busytone r=etienne

(cherry picked from commit d3a918483a7342052ede64bcb5dc6c72f5356212)
Bumping manifests a=b2g-bump