deduplicate the definition of cumprod

Co-authored-by: Matt Thompson <matt.thompson@openforcefield.org>

pint/facets/numpy/numpy_func.py

@@ -965,7 +965,7 @@ def implementation(a, *args, **kwargs):
  return a._REGISTRY.Quantity(func(a_stripped, *args, **kwargs))
 
 
-for func_str in ("cumprod", "cumprod", "nancumprod"):
+for func_str in ("cumprod", "nancumprod"):
  implement_single_dimensionless_argument_func(func_str)
 
 # Handle single-argument consistent unit functions