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

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https://hg.mozilla.org/integration/gaia-central/rev/4d2c0a084832
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #21452 from lissyx/bug1035231

Bug 1035231 - Pass --runtime argument to marionnette

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https://hg.mozilla.org/integration/gaia-central/rev/6ae0d5c5a91e
Author: Alexandre Lissy <lissyx+github@lissyx.dyndns.org>
Desc: Bug 1035231 - Pass --runtime argument to marionnette
Bumping manifests a=b2g-bump