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

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https://hg.mozilla.org/integration/gaia-2_0/rev/278ab0ba1676
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 1025940 - Update self.data_layer.sim_contacts to read SDN Contacts
Bumping manifests a=b2g-bump