Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/703b0d942aad
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 983038 - Play DTMF tones using active call's SIM card on multi-SIM devices r=etienne
Bumping manifests a=b2g-bump