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

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https://hg.mozilla.org/integration/gaia-central/rev/37bba2830c85
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #14134 from pivanov/bug-941628

Bug 941628 - [Settings] Update background and sub header colour

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https://hg.mozilla.org/integration/gaia-central/rev/2b3a8e5e730a
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 941628 - [Settings] Update background and sub header colour