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

========

https://hg.mozilla.org/integration/gaia-central/rev/db0d3d01cb03
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #15256 from borjasalguero/fix_css_settings

Bug 957584 - Incorrect CSS rules in the Settings/Downloads panel r=arctu...

========

https://hg.mozilla.org/integration/gaia-central/rev/194e1084876d
Author: borjasalguero <fbsc@tid.es>
Desc: Bug 957584 - Incorrect CSS rules in the Settings/Downloads panel r=arcturus, kaze
Bumping manifests a=b2g-bump