update whats_new

doc/whats_new.rst

@@ -56,6 +56,7 @@ Detailed list of changes
 
 - When anonymizing the date of a recording, MNE-BIDS will no longer error during `~mne_bids.write_raw_bids` if passing a `~mne.io.Raw` instance to ``empty_room``, by `Daniel McCloy`_ (:gh:`1270`)
 - Dealing with alphanumeric ``sub`` entity labels is now fixed for :func:`~mne_bids.write_raw_bids`, by `Aaron Earle-Richardson`_ (:gh:`1291`)
+- When processing subject_info data that MNE Python imports as numpy arrays with only one item, MNE-BIDS now unpacks these, resulting in a correct participants.tsv, by `Thomas Hartmann`_ (:gh:`1310`)
 
 ⚕️ Code health
 ^^^^^^^^^^^^^^