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

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https://hg.mozilla.org/integration/gaia-central/rev/c6e222c3d864
Author: Sam Foster <sam@sam-i-am.com>
Desc: Merge pull request #23011 from sfoster/bug-1047143-active-app

Bug 1047143 - close aps entering task-manager, exitToApp to open/restore. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/be857a20c625
Author: Sam Foster <sfoster@mozilla.com>
Desc: Bug 1047143 - close aps entering task-manager, exitToApp to open/restore

* Fix assumption that home event means homescreen opens in SoundManager,
* Remove appwillopen handler in AttentionScreen, applaunch will suffice
Bumping manifests a=b2g-bump