Update python/tskit/trees.py

Co-authored-by: Peter Ralph <[email protected]>

python/tskit/trees.py

@@ -7708,8 +7708,8 @@ def genetic_relatedness_weighted(
         :meth:`genetic_relatedness <.TreeSequence.genetic_relatedness>` between sample
             a and sample b, summing over all pairs of samples in the tree sequence.
 
-        :param numpy.ndarray W: An array of values with one row for each sample and one
-            column for each set of weights.
+        :param numpy.ndarray W: An array of values with one row for each sample node and
+            one column for each set of weights.
         :param list indexes: A list of 2-tuples, or None (default). Note that if
             indexes = None, then W must have exactly two columns and this is equivalent
             to indexes = [(0,1)].