[enhancement] add WOCE A16 transect to woce_transects.py

[alicebarthel]

WOCE A16 is the longest North-South Atlantic transect. It would be helpful to have in the standard analysis, especially for WC/AMOC studies.

[xylar]

@alicebarthel, this shouldn't be too hard. It would hopefully just require processing the obs. data by adding another call like this one:
https://github.com/MPAS-Dev/MPAS-Analysis/blob/develop/preprocess_observations/compute_woce_transects.py#L195-L200
then uploading the data to Anvil (LCRC server) and updating setting so that transect also gets plotted.

[xylar]

@alicebarthel, is this something you would like to do before the next MPAS-Analysis release? If so, it would be needed before mid June.