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

========

https://hg.mozilla.org/integration/gaia-central/rev/6dd2c8bd9a82
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #15072 from jmcanterafonseca/sim_export_full

Bug 949594 - [B2G][Contacts] The user will get stuck on the export scree...

========

https://hg.mozilla.org/integration/gaia-central/rev/5dc5e745d1be
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 949594 - [B2G][Contacts] The user will get stuck on the export screen when exporting contacts to the SIM that has no space available for the exported contacts