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

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https://hg.mozilla.org/integration/gaia-central/rev/73633b623dfd
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #15488 from gaye/bug-961192

Bug 961192 - Bump marionette-js-runner version to pick up --verbose fix

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https://hg.mozilla.org/integration/gaia-central/rev/cd7a7021127d
Author: Gareth Aye <gaye@mozilla.com>
Desc: Bug 961192 - Bump marionette-js-runner version to pick up --verbose fix
Bumping manifests a=b2g-bump