Added release note to issue 14401 resolve.

Author: Nicholas Ver Halen

doc/source/whatsnew/v0.19.1.txt

@@ -58,4 +58,5 @@ Bug Fixes
 - Bug in ``df.groupby`` causing an ``AttributeError`` when grouping a single index frame by a column and the index level (:issue`14327`)
 - Bug in ``df.groupby`` where ``TypeError`` raised when ``pd.Grouper(key=...)`` is passed in a list (:issue:`14334`)
 - Bug in ``pd.pivot_table`` may raise ``TypeError`` or ``ValueError`` when ``index`` or ``columns``
-  is not scalar and ``values`` is not specified (:issue:`14380`)
+  is not scalar and ``values`` is not specified (:issue:`14380`)
+- Bug in ``pd.to_numeric`` where a 0 was not unsigned on a downcast = 'unsigned' argument (:issue:`14401`)