fixed rolling func docstring

saqc/funcs/rolling.py

@@ -56,11 +56,6 @@ class RollingMixin:
             sampled timeseries, the period number will be casted down to an odd number if
             ``center=True``.
 
-        target :
-            Field to write the result of the rolling calculation to. Will be generated if not existant.
-            If not given, `field` will be overwritten with the calculations result.
-            If multiple fields are given, `target` must be assigned.
-
         func : default mean
             Function to roll with.