Bumping gaia.json for 4 gaia-central revision(s) a=NPOTB

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https://hg.mozilla.org/integration/gaia-central/rev/684f7deeab97
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #12304 from wanderview/contacts-css-opt

Bug 918174: Load contacts CSS from index.html

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https://hg.mozilla.org/integration/gaia-central/rev/6c981ec2dccd
Author: Ben Kelly <ben@wanderview.com>
Desc: Bug 918174: Load contacts CSS from index.html

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https://hg.mozilla.org/integration/gaia-central/rev/0a88a2ce13e7
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #12290 from jmcanterafonseca/bug-917208

Bug 917208 - [Contacts] Phone field appears twice when merging two conta...

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https://hg.mozilla.org/integration/gaia-central/rev/47e3f76ae9dc
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 917208 - [Contacts] Phone field appears twice when merging two contacts with same phone number