Fix output after cp on large expressions

The expression for cp is grabbed in visual mode, forcing the window to
shift if the entire expression doesn't fit.  Fixing that is hard, so
instead lets just preemptively redraw so a scroll doesn't blow away the
output.

plugin/foreplay.vim

@@ -401,6 +401,7 @@ function! s:opfunc(type) abort
     else
       silent exe "normal! `[v`]y"
     endif
+    redraw
     return @@
   finally
     let @@ = reg_save