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

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https://hg.mozilla.org/integration/gaia-central/rev/4af9ed6ff7ff
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #21945 from yzen/bug-1040290

Bug 1040290 - remedying the visibility conflict between the value select...

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https://hg.mozilla.org/integration/gaia-central/rev/d0cf1ea8dce8
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1040290 - remedying the visibility conflict between the value selector and the system dialog that triggers it.
Bumping manifests a=b2g-bump