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

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https://hg.mozilla.org/integration/gaia-central/rev/c0e6c90d103a
Author: Aleh Zasypkin <aleh.zasypkin@gmail.com>
Desc: Merge pull request #21507 from azasypkin/bug-1035279-errors-mapping

Bug 1035279 - [Messages][Refactoring] Move error codes mapping from dialog.js to a separate file. r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/50e5b702a7be
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 1035279 - [Messages][Refactoring] Move error codes mapping from dialog.js to a separate file. r=julien
Bumping manifests a=b2g-bump