0653/merge plot polar contour

Pull request checklist

Please check if your PR fulfills the following requirements:

[ ] Tests for the changes have been added (for bug fixes / features)
[x ] Docs have been reviewed and added / updated if needed (for bug fixes / features)
- Some docs updates need to be made in the COAsT-site repo, in a separate PR. See contributing to documentation for details.
[x ] Build (./build.sh) was run locally and no errors reported. NB not sure about this requirement: GitActions test this
[x ] Lint (pylint .) has passed locally and any fixes were made for failures. NB not sure about this requirement: GitActions test this with black

Pull request type

Please check the type of change your PR introduces: - [x ] Bugfix - [ ] Feature - [ ] Code style update (formatting, renaming) - [ ] Refactoring (no functional changes, no api changes) - [ ] Build related changes - [ ] Documentation content changes - [ ] Other (please describe): ## What is the current behavior?

The plot_util.plot_polar_contour() function wasn't working as expected. This could be tested using example_scripts\configuration_gallery\gc31_arctic_example_plot.py and looking at the output figure. The contours do not wrap correctly.

Issue URL: #653

What is the new behavior?

The cartopy solution has been put in. A transform=ccrs.epsg(3413) is needed in the .contour() so I've taken out the use of pyproj. This now plots contours correctly with example_scripts\configuration_gallery\gc31_arctic_example_plot.py

Checklist

[x ] Code compiles correctly
[ ] Created tests which fail without the change (if possible)
[x ] All tests passing (pip install . && pytest unit_testing/unit_test.py -s)
[ ] Extended the README / documentation, if necessary
[x ] Added myself / the copyright holder to the AUTHORS file

Does this introduce a breaking change?

[ ] Yes
[x ] No

British-Oceanographic-Data-Centre / COAsT