Bumping gaia.json for 2 gaia-1_3 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_3/rev/50c631bb174d
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 948396 - [Calendar] Can not scroll anymore the week/day view once the new event has been opened with APZ turned on. r=kgrandon

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https://hg.mozilla.org/integration/gaia-1_3/rev/be2fb5f18645
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 942854 - [Calendar] Scrolling the week view results into results into overlapping artifacts. r=kgrandon