vim-patch:8.2.4401: map listing does not clear the rest of the command line

Problem:    Map listing does not clear the rest of the command line.
Solution:   Call msg_clear_eos(). (closes vim/vim#5623, closes vim/vim#5962)
d288eaad84

src/nvim/getchar.c

@@ -3519,6 +3519,7 @@ static void showmap(mapblock_T *mp, bool local)
   if (p_verbose > 0) {
     last_set_msg(mp->m_script_ctx);
   }
+  msg_clr_eos();
   ui_flush();                          // show one line at a time
 }