Remove outdated versionchanged entry
diff --git a/Doc/library/cmath.rst b/Doc/library/cmath.rst
index b50ca5e..cf6fe2c 100644
--- a/Doc/library/cmath.rst
+++ b/Doc/library/cmath.rst
@@ -94,9 +94,6 @@
    specified, returns the natural logarithm of *x*. There is one branch cut, from 0
    along the negative real axis to -∞, continuous from above.
 
-   .. versionchanged:: 2.4
-      *base* argument added.
-
 
 .. function:: log10(x)