xclipman: fix trailing whitespace
xclipman: fix trailing whitespace

Here strings append an ending newline, so this bash doesn't feature
doesn't work here. On the other hand `$()` removes trailing spaces from
the output. So using a variable can't work.

paretje/dotfiles,paretje/dotfiles,paretje/dotfiles,paretje/dotfiles,paretje/dotfiles