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

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https://hg.mozilla.org/integration/gaia-central/rev/06892ffcd552
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #25630 from julienw/1073586-enable-cache

Bug 1073586 - Reenable cache in preferences for DEBUG build r=rickychien

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https://hg.mozilla.org/integration/gaia-central/rev/eae7057b83d7
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1073586 - Reenable cache in preferences for DEBUG build r=rickychien

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https://hg.mozilla.org/integration/gaia-central/rev/7d43256fc4f4
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #25183 from autra/bug1083198

Bug 1083198 : remove fallback code for old gecko in MessageManager.getMessages. r=felash

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https://hg.mozilla.org/integration/gaia-central/rev/fea5fa59d75d
Author: Augustin Trancart <augustin.trancart@gmail.com>
Desc: Bug 1083198 : remove fallback code for old gecko in MessageManager.getMessages
Bumping manifests a=b2g-bump