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

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https://hg.mozilla.org/integration/gaia-central/rev/293d90fe0678
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #13584 from gasolin/issue-937122

Bug 937122 - [UITest] add video permission for API/getUserMedia video te..., r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/4acd214ead6b
Author: gasolin <gasolin@gmail.com>
Desc: Bug 937122 - [UITest] add video permission for API/getUserMedia video test