Revert "Bug 942854 - [Calendar] Scrolling the week view results into results into overlapping artifacts. r=kgrandon"

This reverts commit 78dc0c0013d25de52175e750e4be46bfb2727ef3.
Bug 972666 - [Calendar] lines over events longer than 2 hours
Merge pull request #16621 from millermedeiros/972666-lines-over-events

Bug 972666 - [Calendar] lines over events longer than 2 hours r=gaye