Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/b2ee4c07dd64
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #18524 from JaminLiu/BT_pair_marionette

Bug 968709 - Allow system app to listen to bluetooth-pairing-request. r=echou

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https://hg.mozilla.org/integration/gaia-central/rev/c6bfe7df843a
Author: Jamin Liu <jaliu@mozilla.com>
Desc: Bug 968709 - Allow system app to listen to bluetooth-pairing-request.

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https://hg.mozilla.org/integration/gaia-central/rev/2f5e54c4c0ed
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 881469 - [Messages] Implement Navigation object r=azasypkin,schung

This commit implements a Navigation abstraction to handle navigating between
panels. It also introduces the concept of panels.

Each panel can have 4 lifecycle methods: beforeEnter, afterEnter, beforeLeave,
beforeEnter. These methods either return nothing or a promise.
Bumping manifests a=b2g-bump