Trivial typos

Non-user facing. 
Found using `codespell -q 3`
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index b91ebfa..2a92476 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -227,7 +227,7 @@
 
 
 def test_override_ref():
-    """#392/397: overridding reference-returning functions"""
+    """#392/397: overriding reference-returning functions"""
     o = m.OverrideTest("asdf")
 
     # Not allowed (see associated .cpp comment)