[DOC] Fix latex in trustworthiness docstring
Curly parens were misplaced resulting in an empty sum when rendered.
@@ -441,7 +441,7 @@ def trustworthiness(X, X_embedded, n_neighbors=5, precomputed=False):
.. math::
T(k) = 1 - \frac{2}{nk (2n - 3k - 1)} \sum^n_{i=1}
- \sum_{j \in U^{(k)}_i (r(i, j) - k)}
+ \sum_{j \in U^{(k)}_i} (r(i, j) - k)
where :math:`r(i, j)` is the rank of the embedded datapoint j
according to the pairwise distances between the embedded datapoints,
