plot.py: rewrite using shapely>=2 (OSGeo#3811)

Author: mwtoews

docs/environment.yml

@@ -2,10 +2,9 @@ name: proj
 channels:
   - conda-forge
 dependencies:
-  - descartes
   - geojson
   - matplotlib
-  - shapely < 1.8
+  - shapely >= 2
   - pip
   - pip:
     - breathe