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

========

https://hg.mozilla.org/integration/gaia-central/rev/f1f38950dbdf
Author: gitmai <mri@tid.es>
Desc: Merge pull request #15457 from gitmai/bug-960103-javascript-warning-views-fisttime_css

Bug 960103 - Javascript Warning. Error in parsing value for background. ...
r=salva

========

https://hg.mozilla.org/integration/gaia-central/rev/998b4d2764cb
Author: mai <mri@tid.es>
Desc: Bug 960103 - Javascript Warning. Error in parsing value for background. Declaration dropped. {file: firsttime.css
Bumping manifests a=b2g-bump