Fix typo in dict object comment (GH-15814)

(cherry picked from commit 359143c68659d165f52320d368667e0eff279dc5)

Co-authored-by: dalgarno <32097481+dalgarno@users.noreply.github.com>
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index e417cd2..31f962d 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -39,7 +39,7 @@
 * int32 for 2**16 <= dk_size <= 2**31
 * int64 for 2**32 <= dk_size
 
-dk_entries is array of PyDictKeyEntry.  It's size is USABLE_FRACTION(dk_size).
+dk_entries is array of PyDictKeyEntry.  Its size is USABLE_FRACTION(dk_size).
 DK_ENTRIES(dk) can be used to get pointer to entries.
 
 NOTE: Since negative value is used for DKIX_EMPTY and DKIX_DUMMY, type of