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

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https://hg.mozilla.org/integration/gaia-central/rev/3739122a6a93
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #12433 from steveck-chung/incoming-call-unit-test

Bug 916037 - Follow up bug for writing tests for swiper.js. r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/f856aa05ca0c
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 916037 - Follow up bug for writing tests for swiper.js