Update v0.24.0.txt

Adding BUG pandas-dev#21697

Author: uds5501

doc/source/whatsnew/v0.24.0.txt

@@ -255,6 +255,7 @@ Timezones
 - Bug in :class:`Series` constructor which would coerce tz-aware and tz-naive :class:`Timestamp`s to tz-aware (:issue:`13051`)
 - Bug in :class:`Index` with ``datetime64[ns, tz]`` dtype that did not localize integer data correctly (:issue:`20964`)
 - Bug in :class:`DatetimeIndex` where constructing with an integer and tz would not localize correctly (:issue:`12619`)
+- Bug in :meth:`to_datetime` where Index arg won't retain ``name`` in all cases (:issue:`21697`)
 
 Offsets
 ^^^^^^^