Noted fix for #16583 in WhatsNew

Author: frexvahi

doc/source/whatsnew/v0.20.3.txt

@@ -56,6 +56,7 @@ I/O
 ^^^
 
 -- Bug in ``pd.read_csv()`` in which files weren't opened as binary files by the C engine on Windows, causing EOF characters mid-field, which would fail (:issue:`16039`, :issue:`16559`, :issue`16675`)
+-- Bug in ``pd.read_hdf()`` in which reading a ``Series`` saved to an HDF file in 'fixed' format fails when an explicit ``mode='r'`` argument is supplied (:issue:`16583`)
 
 Plotting
 ^^^^^^^^