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

========

https://hg.mozilla.org/integration/gaia-1_4/rev/68f50ff15399
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #20557 from alivedise/bugzilla/1021583_v1.4/resize-when-app-switch

Bugzilla/1021583 v1.4/resize when app switch, r=timdream

========

https://hg.mozilla.org/integration/gaia-1_4/rev/7f29d0dc9678
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1021583 - Update active app on app switching
Bumping manifests a=b2g-bump