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

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https://hg.mozilla.org/integration/gaia-central/rev/58ad1d392e11
Author: Dietrich Ayala <autonome@gmail.com>
Desc: Merge pull request #14518 from autonome/816133

Bug 816133 - Brightness default value should not be automatic

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https://hg.mozilla.org/integration/gaia-central/rev/4d69d73abd0c
Author: Dietrich Ayala <autonome@gmail.com>
Desc: Bug 816133 - Brightness default value should not be automatic