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

========

https://hg.mozilla.org/integration/gaia-central/rev/6b86712c03eb
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Merge pull request #22542 from jonallengriffin/bug_1039966

Bug 1039966 - Bump marionette_client dep to 0.8.1

========

https://hg.mozilla.org/integration/gaia-central/rev/984773ee0479
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Bug 1039966 - Bump marionette_client dep to 0.8.1
Bumping manifests a=b2g-bump