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

========

https://hg.mozilla.org/integration/gaia-central/rev/84b895ff4787
Author: GaryChen,PYChen <mmm198219@gmail.com>
Desc: Merge pull request #18974 from mpizza/bug_979785_overwrite_settings_by_device_type

Bug 979785 - [GAIA][BUILD SYSTEM] Overwrite common-setting.json by GAIA_DEVICE_TYPE in build/settings.js. r=yurenju.

========

https://hg.mozilla.org/integration/gaia-central/rev/2477ea0caadb
Author: mpizza <mmm198219@gmail.com>
Desc: Bug 979785 - [GAIA][BUILD SYSTEM] Overwrite common-setting.json by GAIA_DEVICE_TYPE in build/settings.js
Bumping manifests a=b2g-bump