update readme

After testing nerdtree, it seems the window might be messed up
if the user is not careful

README.md

@@ -56,5 +56,4 @@ nnoremap <leader>n :LuaTreeRefresh<CR>
 - use libuv functions instead of `touch` and `mkdir` in `create_file()` and allow file creation with path like `foo/bar/baz`
 - cd command to move faster accross the fs if needed
 - quickly find file in the directory structure
-- tree should always stay on the side
 - html docs