This test requirement is superfluous.

--- readme_renderer-44.0/tox.ini.orig
+++ readme_renderer-44.0/tox.ini
@@ -14,7 +14,6 @@
 deps =
     pytest
     pytest-cov
-    pytest-icdiff
 setenv =
     # Display up to 20 frames in backtraces when showing ResourceWarnings.
     PYTHONTRACEMALLOC=20