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

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https://hg.mozilla.org/integration/gaia-central/rev/c79ce4a07c3f
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #12770 from jmcanterafonseca/fix_924244

Bug 924244 - [B2G][Contacts] After exporting a contact the UI still disp...

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https://hg.mozilla.org/integration/gaia-central/rev/62678797d5a9
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 924244 - [B2G][Contacts] After exporting a contact the UI still displays Export in the top right