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

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https://hg.mozilla.org/integration/gaia-central/rev/e246a2dd28bb
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #22429 from yzen/bug-1047497

Bug 1047497 - fixed screen reader visibility issue with software buttons...

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https://hg.mozilla.org/integration/gaia-central/rev/91c2637140e9
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1047497 - fixed screen reader visibility issue with software buttons. Added tests to avoid future regressions.
Bumping manifests a=b2g-bump