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

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https://hg.mozilla.org/integration/gaia-central/rev/90808de32b4f
Author: Ghislain 'Aus' Lacroix <aus@noiseport.org>
Desc: Merge pull request #15089 from nullaus/bug952305-net-error

bug 952305

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https://hg.mozilla.org/integration/gaia-central/rev/52cf1a3ecd95
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 952305

* use default gecko error message for all errors for which we do not have special handling.
** currently this means for all errors other than netOffline and dnsNotFound.

r=mhenretty