Bumping gaia.json for 5 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/263a2102c567
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #20777 from yor-mozilla-com/gaia-header-keyboard

Bug 1015295 - [Keyboard] Update to use gaia-header

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https://hg.mozilla.org/integration/gaia-central/rev/576ca02203ec
Author: Yan Or <yor@mozilla.com>
Desc: Bug 1015295 - [Keyboard] Update to use gaia-header

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https://hg.mozilla.org/integration/gaia-central/rev/dcb799e2eb6b
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #21300 from Rik/csslint-in-travis

Bug 1024993 - Run the CSS Linter in Travis/TBPL r=ochameau

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https://hg.mozilla.org/integration/gaia-central/rev/473ceea4e543
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 1024993 - Update CSS xfail list to be green

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https://hg.mozilla.org/integration/gaia-central/rev/a2200bcc8705
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 1024993 -  Run the CSS Linter in Travis/TBPL

Refactor the script to only report unknown problems
Bumping manifests a=b2g-bump