cs_print_tags_priv: Clear first output line to screen end

Using `:cscope find s <cword>` with the cursor on a very short word like
`key` does not output the first line on the screen correctly: Output is
`Cscope tag: keyrd>` instead of
`Cscope tag: key`.

To fix this, clear the screen line after the first line was printed.

src/nvim/if_cscope.c

@@ -1667,6 +1667,7 @@ static void cs_print_tags_priv(char **matches, char **cntxts,
   size_t bufsize = newsize;  // Track available bufsize
   (void)sprintf(buf, cstag_msg, ptag);
   MSG_PUTS_ATTR(buf, hl_attr(HLF_T));
+  msg_clr_eos();
 
   // restore matches[0]
   *ptag_end = '\t';