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

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https://hg.mozilla.org/integration/gaia-central/rev/357ede163d03
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #20923 from pivanov/bug-1029382

Bug 1029382 - [Gallery] [Flame]- Back arrow button shows too large in high resolution devices.

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https://hg.mozilla.org/integration/gaia-central/rev/c6ce541e1c1f
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 1029382 - [Gallery] [Flame]- Back arrow button shows too large in high resolution devices.
Bumping manifests a=b2g-bump