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

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https://hg.mozilla.org/integration/gaia-central/rev/77593e7e3a4f
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #19564 from yzen/bug-1014775

Bug 1014775 - adding aria-live to notification toasters so they are anno...

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https://hg.mozilla.org/integration/gaia-central/rev/6deedb0312da
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1014775 - adding aria-live to notification toasters so they are announced with the screen reader.
Bumping manifests a=b2g-bump