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

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https://hg.mozilla.org/integration/gaia-central/rev/42689e15ce61
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #21360 from yzen/bug-962434

Bug 962434 - Moving value selector into subcomponents of an appWindow. I...

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https://hg.mozilla.org/integration/gaia-central/rev/72f28b8f6b20
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 962434 - Moving value selector into subcomponents of an appWindow. Improving its visibility a11y. r=alive
Bumping manifests a=b2g-bump