Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/6c6f05ce626b
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Bug 993095 - Remove extra quotation mark that was added accidentally.
Bumping manifests a=b2g-bump