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

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https://hg.mozilla.org/integration/gaia-central/rev/c2988aaa4cf4
Author: Ben Kelly <bkelly@mozilla.com>
Desc: Merge pull request #11014 from wanderview/contacts-update-delete

Bug 894302: Support contact delete during update activity.  r=arcturus

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https://hg.mozilla.org/integration/gaia-central/rev/d604f1745349
Author: Ben Kelly <ben@wanderview.com>
Desc: Bug 894302: Support contact delete during update activity.