TST: Update contour test limits

Partial cherry-pick of 579be04
to increase the test tolerance of the images for MPL3.5 tests.

Author: greglucas

.github/workflows/ci-testing.yml

@@ -34,7 +34,7 @@ jobs:
       - name: Latest packages
         if: steps.minimum-packages.conclusion == 'skipped'
         run: |
-          echo "PACKAGES=cython fiona matplotlib-base numpy pyproj pykdtree scipy shapely" >> $GITHUB_ENV
+          echo "PACKAGES=cython fiona matplotlib-base numpy pyproj 'proj>=8' pykdtree scipy shapely" >> $GITHUB_ENV
 
       - name: Coverage packages
         id: coverage

lib/cartopy/tests/mpl/test_mpl_integration.py

@@ -19,7 +19,7 @@
 
 # This is due to a change in MPL 3.5 contour line paths changing
 # ever so slightly.
-contour_tol = 2.24
+contour_tol = 2.25
 @pytest.mark.natural_earth
 @ImageTesting(['global_contour_wrap'], style='mpl20',
               tolerance=contour_tol)