Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/74f70f3c2504
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1043293 - [Verticalhome] use "touchend" instead of "click" to launch applications r=kgrandon

* attach the scroll event on the main window
* remove stopImmediatePropagation from some locations so that the contextmenu
  event can be received by the grid
* if the event is defaultPrevented, we don't do the default action, that is
  neither drag&drop (edit mode) or launch an app
Bumping manifests a=b2g-bump