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

========

https://hg.mozilla.org/integration/gaia-central/rev/387455fe64df
Author: Carmen Jiménez <carmen.jimenezcabezas@telefonica.com>
Desc: Merge pull request #23640 from mcjimenez/bug1061750

Bug 1061750 - SV Build: Generate the configuration file for bookmarks (r = yurenju)

========

https://hg.mozilla.org/integration/gaia-central/rev/7db310555def
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 1061750 - SV Build: Generate the configuration file for bookmarks
Bumping manifests a=b2g-bump