Fix one new style error introduced in scaladoc warning commit

Author: srowen

core/src/main/scala/org/apache/spark/util/StatCounter.scala

@@ -19,8 +19,9 @@ package org.apache.spark.util
 
 /**
  * A class for tracking the statistics of a set of numbers (count, mean and variance) in a
- * numerically robust way. Includes support for merging two StatCounters. Based on 
- * [[http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance Welford and Chan's algorithms for running variance]].
+ * numerically robust way. Includes support for merging two StatCounters. Based on Welford
+ * and Chan's [[http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance algorithms]]
+ * for running variance.
  *
  * @constructor Initialize the StatCounter with the given values.
  */