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

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https://hg.mozilla.org/integration/gaia-central/rev/81abf4c4d385
Author: Rex KM Lee <rexboy@mozilla.com>
Desc: Merge pull request #14113 from rexboy7/fix-bug933153

Bug 933153 - hold active call before making another call. r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/92f892161774
Author: Rex Lee <rexboy@mozilla.com>
Desc: Bug 933153 - hold active call before making another call