fix: redraw after setting fdm

Problem:
Setting fdm itself doesn't seem to trigger recomputation of fold.

Solution:
Explicitly redraw to force fold recomputation.

Author: tomtomjhj

plugin/fastfold.vim

@@ -66,6 +66,10 @@ function! s:LeaveWin()
   if exists('w:lastfdm') && &l:foldmethod is# 'manual'
     let &l:foldmethod = w:lastfdm
   endif
+
+  if exists('*win_execute')
+      redraw
+  endif
 endfunction
 
 " Like :windo, but restores the current window and avoids side effects.