notes.h: fix typos in comment

In 1d7297513d (notes: break set_display_notes() into smaller functions,
2019-12-11), we introduced a comment which had a couple of typos. In the
first typo, we referenced 'enable_default_display_notes' instead of
'enable_ref_display_notes'. In the second typo, we wrote "is a points to"
instead of "is a pointer to". Correct both of these typos.

Reported-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.h

@@ -268,11 +268,11 @@ void init_display_notes(struct display_notes_opt *opt);
 /*
  * This family of functions enables or disables the display of notes. In
  * particular, 'enable_default_display_notes' will display the default notes,
- * 'enable_default_display_notes' will display the notes ref 'ref' and
+ * 'enable_ref_display_notes' will display the notes ref 'ref' and
  * 'disable_display_notes' will disable notes, including those added by previous
  * invocations of the 'enable_*_display_notes' functions.
  *
- * 'show_notes' is a points to a boolean which will be set to 1 if notes are
+ * 'show_notes' is a pointer to a boolean which will be set to 1 if notes are
  * displayed, else 0. It must not be NULL.
  */
 void enable_default_display_notes(struct display_notes_opt *opt, int *show_notes);