Log Message:
py-contourpy: update to 1.2.0.

v1.2.0 (2023-11-03)
-------------------

ContourPy 1.2.0 is a significant release with a number of new
features. There is a new format for contour lines called
``LineType.ChunkCombinedNan`` that is designed to work directly
with Bokeh and HoloViews. There are also new functions for manipulating
contour lines and filled contours (``convert_filled``, ``convert_lines``,
``dechunk_filled`` and ``dechunk_lines``).

Calling ``ContourGenerator.filled()`` with two identical levels
now raises a ``ValueError`` whereas previously it gave different
results depending on algorithm ``name``.