Update the test_subplot_outside_plotting_positioning test and increas…

…e the RMS tolerance (#2454)

Co-authored-by: Wei Ji <23487320+weiji14@users.noreply.github.com>

pygmt/tests/test_subplot.py

@@ -102,7 +102,9 @@ def test_subplot_nrows_ncols_less_than_one_error():
             pass
 
 
-@pytest.mark.mpl_image_compare
+# Increase tolerance for compatibility with GMT 6.3 and 6.4, see
+# https://github.com/GenericMappingTools/pygmt/pull/2454
+@pytest.mark.mpl_image_compare(tolerance=4.0)
 def test_subplot_outside_plotting_positioning():
     """
     Plotting calls are correctly positioned after exiting subplot.
@@ -112,7 +114,7 @@ def test_subplot_outside_plotting_positioning():
     """
     fig = Figure()
     with fig.subplot(nrows=1, ncols=2, figsize=(10, 5)):
-        fig.basemap(region=[0, 10, 0, 10], projection="X?", frame=True, panel=True)
-        fig.basemap(region=[0, 10, 0, 10], projection="X?", frame=True, panel=True)
+        fig.basemap(region=[0, 10, 0, 10], projection="X?", panel=True)
+        fig.basemap(region=[0, 10, 0, 10], projection="X?", panel=True)
     fig.colorbar(position="JBC+w5c+h", cmap="turbo", frame=True)
     return fig