Bumping gaia.json for 3 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/a11b254563d2
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #10469 from eeejay/lockscreen-a11y-tweaks

Bug 884514, 884517 - Lockscreen a11y tweaks

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https://hg.mozilla.org/integration/gaia-central/rev/cb45fd51a8f0
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 884514 - Hide windows when lockscreen is active.

Changing the style of the app iframes won't work well because it will interfere with the way that audio apps work. So we need to use aria-hidden.

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https://hg.mozilla.org/integration/gaia-central/rev/f31603695163
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 884517 - Change lockscreen to not collapse button area when screenreader is enabled.

Updates:
 - Conditionally remove 'triggered' class when screen reader is disabled.
 - Also deleted some obsolete 'triggered' class removal lines that followed.