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

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https://hg.mozilla.org/integration/gaia-central/rev/155f5ff682e5
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #24360 from KevinGrandon/bug_1071953_app_launching_visibility_cases

Bug 1071953 - [Rocketbar] Tweak visibility controls for open-window.show App and apploading.stayBackground

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https://hg.mozilla.org/integration/gaia-central/rev/b0cabb7e8ba1
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1071953 - [Rocketbar] Tweak visibility controls for open-window.showApp and apploading.stayBackground r=alive
Bumping manifests a=b2g-bump