webui: Render upcoming recording duplicates with a line-through in grid. (#4632)

webui: Render upcoming recording duplicates with a line-through in grid. (#4632)

The advanced and expert views on the upcoming tab have a column for the
duplicate date. But on the basic view there is no indication of
duplicates unless you click information on the entry.

So we now render duplicates with a line-through. This makes it clear
they are duplicates that will not be recorded.

Issue: #4632