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

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https://hg.mozilla.org/integration/gaia-central/rev/5af1d86d5f6c
Author: Carmen Jiménez <cjc@tid.es>
Desc: Merge pull request #18752 from mcjimenez/bug1001212

Bug 1001212 - Cannot preinstall a packaged app that has a mini-manifest using a package_path that is a relative path.

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https://hg.mozilla.org/integration/gaia-central/rev/5cb6a965c7cb
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 1001212 - Cannot preinstall a packaged app that has a mini-manifest using a package_path that is a relative path

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https://hg.mozilla.org/integration/gaia-central/rev/31e27a24f100
Author: Ben Francis <ben@tola.me.uk>
Desc: Merge pull request #18810 from daleharvey/998118

Bug 998118 - Dont display crashed background tabs. r=benfrancis

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https://hg.mozilla.org/integration/gaia-central/rev/42d2303076fb
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 998118 - Dont display crashed background tabs. r=benfrancis
Bumping manifests a=b2g-bump