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

========

https://hg.mozilla.org/integration/gaia-central/rev/517577255b59
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #13085 from gasolin/issue-929889

Bug 929889 - Remove 'portrait-primary' lock in system app, r=alive

========

https://hg.mozilla.org/integration/gaia-central/rev/2f7414bc9ec6
Author: gasolin <gasolin@gmail.com>
Desc: Bug 929889 - Remove 'portrait-primary' lock in system app