Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/c72e86becabc
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #23974 from KevinGrandon/bug_1066307_task_manager_initial_landscape_sizing

Bug 1066307 - [TaskManager] Update initial sizing when entering from landscape mode

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https://hg.mozilla.org/integration/gaia-central/rev/7ee38ec462fa
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1066307 - [TaskManager] Update initial sizing when entering from landscape mode r=vingtetun

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https://hg.mozilla.org/integration/gaia-central/rev/a3d06a19ceeb
Author: albertopq <albert.pastor@gmail.com>
Desc: Merge pull request #23927 from albertopq/1062334-color-ambient

Bug 1062334 - Update ambient indicator colour r=mhenretty

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https://hg.mozilla.org/integration/gaia-central/rev/f77033f309ce
Author: albertopq <apastor@mozilla.com>
Desc: Bug 1062334 - Update ambient indicator colour
Bumping manifests a=b2g-bump