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

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https://hg.mozilla.org/integration/gaia-central/rev/a88fd2441357
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #22068 from mancas/bug929311

Bug929311 - Should provide more suitable description while user want to download the updates in roaming area . r=jlee

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https://hg.mozilla.org/integration/gaia-central/rev/5e4d0d1704c0
Author: Manuel Casas Barrado <b.mcb@tid.es>
Desc: Bug 929311 - Should provide more suitable description while user want to download the updates in roaming area

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https://hg.mozilla.org/integration/gaia-central/rev/5989b9f1b4fe
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #21805 from mancas/bug798254

Bug 798254 - [Settings] Prompt the user when switching on two incompatib...r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/471002770fcb
Author: Manuel Casas Barrado <b.mcb@tid.es>
Desc: Bug 798254 - [Settings] Prompt the user when switching on two incompatible settings
Bumping manifests a=b2g-bump