Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_4/rev/bce3d01a3312
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #20927 from comoyo/bug995886_v1_4

Bug 995886 - Homescreens overlap when process is killed when screen is off

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https://hg.mozilla.org/integration/gaia-1_4/rev/6f0d403da5fa
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Bug 995886 - Homescreens overlap when process is killed when screen is off

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https://hg.mozilla.org/integration/gaia-1_4/rev/7a00b200649d
Author: crdlc <crdlc@tid.es>
Desc: Bug 991906 - [B2G][Homescreen] Long pressing an App that opened in Landscape mode will cause the Dock apps to shift

Conflicts:
	apps/homescreen/js/grid.js
Bumping manifests a=b2g-bump