Apply suggestions from code review

Co-authored-by: Peter Ralph <petrel.harp@gmail.com>

Author: apragsdale

docs/stats.md

@@ -774,7 +774,7 @@ tree, the specified positions must land in the tree span (`[start, end)`).
 
 In the following, we compute a matrix of expected {math}`r^2` within and
 between the first 4 trees in the tree sequence. The tree breakpoints are
-a convenient way to specify those first four trees tree.
+a convenient way to specify those first four trees.
 
 ```{code-cell} ipython3
 ld = ts.ld_matrix(mode="branch", positions=[ts.breakpoints(as_array=True)[0:4]])