TST: Set tests touched by text overhaul to mpl20 style (matplotlib#31300)

* TST: Set tests touched by text overhaul to mpl20 style

* TST: Tweak some tests to work better in mpl20 style

Author: QuLogic

lib/matplotlib/tests/test_agg_filter.py

@@ -5,7 +5,7 @@
 
 
 @image_comparison(baseline_images=['agg_filter_alpha'],
-                  extensions=['gif', 'png', 'pdf'])
+                  extensions=['gif', 'png', 'pdf'], style='mpl20')
 def test_agg_filter_alpha():
     ax = plt.axes()
     x, y = np.mgrid[0:7, 0:8]

lib/matplotlib/tests/test_arrow_patches.py

@@ -28,7 +28,7 @@ def test_fancyarrow():
             ax.tick_params(labelleft=False, labelbottom=False)
 
 
-@image_comparison(['boxarrow_test_image.png'])
+@image_comparison(['boxarrow_test_image.png'], style='mpl20')
 def test_boxarrow():
 
     styles = mpatches.BoxStyle.get_styles()