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

========

https://hg.mozilla.org/integration/gaia-central/rev/6f862d265c06
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #15442 from steveck-chung/bug-948958

Bug 948958 - [Messages][MMS] MMS does not display correctly when it has a subject but no content

========

https://hg.mozilla.org/integration/gaia-central/rev/36ca9b74c9ba
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 948958 - [Messages][MMS] MMS does not display correctly when it has a subject but no content
Bumping manifests a=b2g-bump