Fix PEP8 W293

blank line contains whitespace

test/TestColors.py

@@ -69,7 +69,7 @@ class ColorsTest(TopydoTest):
         color = Colors().get_context_color()
 
         self.assertEqual(color, NEUTRAL_COLOR)
-    
+
     def test_metadata_color1(self):
         config(p_overrides={('colorscheme', 'metadata_color'): '128'})
         color = Colors().get_metadata_color()