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

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https://hg.mozilla.org/integration/gaia-central/rev/104c9cea36f8
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #22371 from yzen/bug-1030465

Bug 1030465 - use 'accessibility.screenreader-volume' for both sounds an...

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https://hg.mozilla.org/integration/gaia-central/rev/78a990fbfd73
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1030465 - use 'accessibility.screenreader-volume' for both sounds and speech. Handle mute efficiently. Take into account speech synthesis volumes. Updated and added more accessibility.js unit tests. r=alive
Bumping manifests a=b2g-bump