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

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https://hg.mozilla.org/integration/gaia-central/rev/8f39be7efe62
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #23014 from eeejay/bug-1055356

Bug 1055356 - Make the 'unread' flag and contact photo screen reader vis... r=azasypkin

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https://hg.mozilla.org/integration/gaia-central/rev/ece6935c7b84
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 1055356 - Make the 'unread' flag and contact photo screen reader visible.
Bumping manifests a=b2g-bump