Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/8ecdae39a8b0
Author: Casey Yee <cyee@mozilla.com>
Desc: Merge pull request #14151 from Joshua-S/bug-941631

[Bug 941631] - [Cost Control] Update background and sub header colour [r=salva]

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https://hg.mozilla.org/integration/gaia-central/rev/443bb7c84527
Author: Joshua Smith <joshua-smith@verizon.net>
Desc: Bug 941631 - [Cost Control] Update background and sub header colour

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https://hg.mozilla.org/integration/gaia-central/rev/86167748e300
Author: Casey Yee <cyee@mozilla.com>
Desc: Merge pull request #14144 from Joshua-S/bug-941632

[Bug 941632] - [Email] Update background and sub header colour [r+=jrburke]

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https://hg.mozilla.org/integration/gaia-central/rev/6f4ad24ee6d7
Author: Joshua Smith <joshua-smith@verizon.net>
Desc: Bug 941632 - [Email] Update background and sub header colour