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

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https://hg.mozilla.org/integration/gaia-1_4/rev/151e0c8edf52
Author: PinZhang <zhangpin04@gmail.com>
Desc: Merge pull request #22288 from PinZhang/pzhang/bug1042478-v1.4

Bug 1042478: AirplaneModeHelper.ready is invoked several. r=ejchen

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https://hg.mozilla.org/integration/gaia-1_4/rev/73e96c2bb020
Author: Pin Zhang <pzhang@mozilla.com>
Desc: Bug 1042478: AirplaneModeHelper.ready is invoked several
Bumping manifests a=b2g-bump