This test requirement is superfluous.

--- readme_renderer-45.0/tox.ini.orig
+++ readme_renderer-45.0/tox.ini
@@ -15,7 +15,6 @@
 deps =
     pytest
     pytest-cov
-    pytest-icdiff
 commands =
     pytest -Wall --strict-markers --cov {posargs}
 extras = md