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

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https://hg.mozilla.org/integration/gaia-central/rev/6e59fa03abdb
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #23046 from yzen/bug-1053193

Bug 1053193 - cropped beginning silence from a11y sound files. Updated t...

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https://hg.mozilla.org/integration/gaia-central/rev/7356bc45a128
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1053193 - cropped beginning silence from a11y sound files. Updated the way a11y sounds are played by the accessibility component.
Bumping manifests a=b2g-bump