[RFC] Remove `~` after end-of-line

Hey,

this replaces the `~` shown after the last line in the file by a space.

I'd argue that this character is useless and many people either just put up with it or change the `NonText` highlight group so that foreground and background have the same color. But the problem with the latter "solution" is that `NonText` also gets used for some characters from the `'listchars'` option where it would be useful to actually see them.. :-)