DOC: fixed ref

Author: TomAugspurger

doc/source/whatsnew/v0.25.0.rst

@@ -1186,7 +1186,7 @@ ExtensionArray
 - :meth:`Series.count` miscounts NA values in ExtensionArrays (:issue:`26835`)
 - Added ``Series.__array_ufunc__`` to better handle NumPy ufuncs applied to Series backed by extension arrays (:issue:`23293`).
 - Keyword argument ``deep`` has been removed from :meth:`ExtensionArray.copy` (:issue:`27083`)
-- Allow parsing of `PeriodDType` columns when using `read_csv()` (:issue:`26934`)
+- Allow parsing of :class:`PeriodDtype` columns when using `read_csv()` (:issue:`26934`)
 
 Other
 ^^^^^