MNT: Clean up out-dated handling for older dep versions

Not needed since we dropped support for these older versions.

Author: dopplershift

src/metpy/units.py

@@ -75,10 +75,6 @@ def setup_registry(reg):
         if pre not in reg.preprocessors:
             reg.preprocessors.append(pre)
 
-    # Add a percent unit if it's not already present, it was added in 0.21
-    if 'percent' not in reg:
-        reg.define('percent = 0.01 = %')
-
     # Define commonly encountered units not defined by pint
     reg.define('degrees_north = degree = degrees_N = degreesN = degree_north = degree_N '
                '= degreeN')

tests/calc/test_indices.py

@@ -131,7 +131,6 @@ def test_weighted_continuous_average():
     assert_almost_equal(v, 6.900543760612305 * units('m/s'), 7)
 
 
-@pytest.mark.xfail(condition=version_check('pint<0.21'), reason='hgrecco/pint#1593')
 def test_weighted_continuous_average_temperature():
     """Test pressure-weighted mean temperature function with vertical interpolation."""
     data = get_upper_air_data(datetime(2016, 5, 22, 0), 'DDC')

tests/plots/test_skewt.py

@@ -321,8 +321,7 @@ def test_hodograph_api():
     return fig
 
 
-@pytest.mark.mpl_image_compare(
-    remove_text=True, tolerance=0.6 if version_check('matplotlib==3.5') else 0.)
+@pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.)
 def test_hodograph_units():
     """Test passing quantities to Hodograph."""
     fig = plt.figure(figsize=(9, 9))

tests/plots/test_util.py

@@ -90,9 +90,7 @@ def test_add_logo_invalid_size():
         add_metpy_logo(fig, size='jumbo')
 
 
-@pytest.mark.mpl_image_compare(
-    tolerance=1.072 if version_check('matplotlib<3.5') else 0,
-    remove_text=True)
+@pytest.mark.mpl_image_compare(tolerance=0, remove_text=True)
 def test_gempak_color_image_compare():
     """Test creating a plot with all the GEMPAK colors."""
     c = range(32)
@@ -111,9 +109,7 @@ def test_gempak_color_image_compare():
     return fig
 
 
-@pytest.mark.mpl_image_compare(
-    tolerance=1.215 if version_check('matplotlib<3.5') else 0,
-    remove_text=True)
+@pytest.mark.mpl_image_compare(tolerance=0, remove_text=True)
 def test_gempak_color_xw_image_compare():
     """Test creating a plot with all the GEMPAK colors using xw style."""
     c = range(32)