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

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https://hg.mozilla.org/integration/gaia-central/rev/da768a6739ce
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #23797 from mancas/bug1062326

Bug 1062326 - [FTE] Status bar should be dark on dark FTE screens. r=fcampo

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https://hg.mozilla.org/integration/gaia-central/rev/31a3a88f8442
Author: Manuel Casas Barrado <manuel.casasbarrado@telefonica.com>
Desc: Bug 1062326 - [FTE] Status bar should be dark on dark FTE screens
Bumping manifests a=b2g-bump