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

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https://hg.mozilla.org/integration/gaia-central/rev/87b13252a973
Author: Arthur Chen <crh0716@gmail.com>
Desc: Revert "Bug 975918 - Support DSDS for voice mail"

This reverts commit 9624c4d03cbbd4042cf26d2e56c42b58849b4c5f.
Bumping manifests a=b2g-bump