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

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https://hg.mozilla.org/integration/gaia-central/rev/3d86f253ab4a
Author: Ting-Yu Chou <janus926@gmail.com>
Desc: Bug 1087905 - Limit the scope of sound_manager.css to avoid affecting #windows div with :nth-last-child(). r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/7ee99895e241
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Revert "Merge pull request #25436 from janus926/bug-1087905"

This reverts commit 64f4a6fa02e16140e005b3ec1195c90a6a698aeb, reversing
changes made to bfbd561aff39154d65ef9891ce3f8bc9e9c5e44c.
Bumping manifests a=b2g-bump