Update EnumeratedDistribution.java (#166)

Fix typo in description
diff --git a/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java b/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
index 27f53bd..5ecbdf4 100644
--- a/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
+++ b/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
@@ -45,7 +45,7 @@
  * contain null values.  The pmf created by the constructor will combine probabilities of equal values and
  * will treat null values as equal.  For example, if the list of pairs <"dog", 0.2>, <null, 0.1>,
  * <"pig", 0.2>, <"dog", 0.1>, <null, 0.4> is provided to the constructor, the resulting
- * pmf will assign mass of 0.5 to null, 0.3 to "dog" and 0.2 to null.</p>
+ * pmf will assign mass of 0.5 to null, 0.3 to "dog" and 0.2 to pig.</p>
  *
  * @param <T> type of the elements in the sample space.
  * @since 3.2