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

========

https://hg.mozilla.org/integration/gaia-central/rev/972f21a6c00f
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19412 from KevinGrandon/bug_1013085_gaia_header_naming

Bug 1013085 - change gaia-header folder name

========

https://hg.mozilla.org/integration/gaia-central/rev/89291145614a
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1013085 - change gaia-header folder name r=yor r=wilsonpage
Bumping manifests a=b2g-bump