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

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https://hg.mozilla.org/integration/gaia-1_4/rev/faf480183308
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Merge pull request #17360 from prcxuying/bug972308

Bug 972308 - Re-use the existing Audio object when playing keypad tones r=gsvelto
Bumping manifests a=b2g-bump