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

========

https://hg.mozilla.org/integration/gaia-central/rev/dffc91b36d29
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #25329 from bnjbvr/arraybuf

Bug 997973 - Fix Gaia consumers that call typed array constructors without "new"; r=etienne

========

https://hg.mozilla.org/integration/gaia-central/rev/91cfcf9834a0
Author: Benjamin Bouvier <public@benj.me>
Desc: Bug 997973 - Fix Gaia consumers that call typed array constructors without "new"; r=etienne
Bumping manifests a=b2g-bump