ComponentEditor size test fails on Windows and Wx

Currently there is one test failure on the wx + Windows CI job:
```
======================================================================
FAIL: test_initial_component_with_item_size (enable.tests.test_component_editor.TestComponentEditor)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Users\appveyor\.edm\envs\enable-test-3.6-wx-pillow\lib\site-packages\enable\tests\test_component_editor.py", line 65, in test_initial_component_with_item_size
self.assertLess(size[1], ITEM_HEIGHT+30)
AssertionError: 241 not less than 230
```

(In #459, I failed to notice there is a wx job on Appveyor that is currently allowed to fail.)