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

========

https://hg.mozilla.org/integration/gaia-central/rev/818396a1e2e6
Author: Ben Francis <ben@tola.me.uk>
Desc: Merge pull request #21055 from benfrancis/1021385

Bug 1021385 - Open link in new tab from wrapper should open in browser r=daleharvey

========

https://hg.mozilla.org/integration/gaia-central/rev/8954bc9ab13b
Author: Ben Francis <ben@tola.me.uk>
Desc: Bug 1021385 - Open link in new tab from wrapper should open in browser
Bumping manifests a=b2g-bump