Fix typo in dict object comment (#15814)

Fix typo in dict object comment (#15814) · python/cpython@359143c

Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,7 @@ Size of indices is dk_size. Type of each index in indices is vary on dk_size:`
`39`	`39`	`* int32 for 216 <= dk_size <= 231`
`40`	`40`	`* int64 for 2**32 <= dk_size`
`41`	`41`
`42`		`-dk_entries is array of PyDictKeyEntry. It's size is USABLE_FRACTION(dk_size).`
	`42`	`+dk_entries is array of PyDictKeyEntry. Its size is USABLE_FRACTION(dk_size).`
`43`	`43`	`DK_ENTRIES(dk) can be used to get pointer to entries.`
`44`	`44`
`45`	`45`	`NOTE: Since negative value is used for DKIX_EMPTY and DKIX_DUMMY, type of`