Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/631751ac7bb9
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 950795 - [Messages] Reduce the use of ids in the "you received a message" notice r=schung

========

https://hg.mozilla.org/integration/gaia-central/rev/b89d57c6f6c3
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #15614 from jrburke/bug962761-email-attachment-l10n-name

Bug 962761 - [email] better l10n string for default attachment name r=asuth

========

https://hg.mozilla.org/integration/gaia-central/rev/98cfcda19383
Author: jrburke <jrburke@gmail.com>
Desc: Bug 962761 - [email] better l10n string for default attachment name
Bumping manifests a=b2g-bump