Fix notebooks/Dfsu - Export to shapefile.ipynb not compatible with matplotlib 3.10

[ecomodeller]

https://pypi.org/project/matplotlib/3.10.0/

for collection,level in zip(cn.collections,contour_levels):
    for p in collection.get_paths():
        v = p.vertices
        x = v[:,0]
        y = v[:,1]
        poly = LineString([(i[0], i[1]) for i in zip(x,y)])
        if(poly.is_empty):
            print(f"{i} is empty")
        poly_list.append(dict(wind_speed = level, poly = poly))
------------------


---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[13], line 5
      1 from shapely.geometry import LineString
      3 poly_list = []
----> 5 for collection,level in zip(cn.collections,contour_levels):
      6     for p in collection.get_paths():
      7         v = p.vertices

AttributeError: 'QuadContourSet' object has no attribute 'collections