DOC Fix typo in manifold documentation (#14073)

Johann Faouzi · rth · commit 9c732e15a89b · 2019-06-12T14:19:30.000+02:00
diff --git a/doc/modules/manifold.rst b/doc/modules/manifold.rst
@@ -509,7 +509,7 @@ The disadvantages to using t-SNE are roughly:
 * The algorithm is stochastic and multiple restarts with different seeds can
   yield different embeddings. However, it is perfectly legitimate to pick the
   embedding with the least error.
-* Global structure is not explicitly preserved. This is problem is mitigated by
+* Global structure is not explicitly preserved. This problem is mitigated by
   initializing points with PCA (using `init='pca'`).
 
 
