Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/387f4c0123a7
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1026992 - [FTU] Several issues in navigation_test.js r=fcampo
Bumping manifests a=b2g-bump