[SPARK-9530] [MLLIB] ScalaDoc should not indicate LDAModel.describeTopics and...

[SPARK-9530] [MLLIB] ScalaDoc should not indicate LDAModel.describeTopics and DistributedLDAModel.topDocumentsPerTopic as approximate

Remove ScalaDoc that suggests describeTopics and topDocumentsPerTopic are approximate.

cc jkbradley

Author: Meihua Wu <meihuawu@umich.edu>

Closes #7858 from rotationsymmetry/SPARK-9530 and squashes the following commits:

b574923 [Meihua Wu] Remove ScalaDoc that suggests describeTopics and topDocumentsPerTopic are approximate.

mllib/src/main/scala/org/apache/spark/mllib/clustering/LDAModel.scala

@@ -86,10 +86,6 @@ abstract class LDAModel private[clustering] extends Saveable {
   /**
    * Return the topics described by weighted terms.
    *
-   * This limits the number of terms per topic.
-   * This is approximate; it may not return exactly the top-weighted terms for each topic.
-   * To get a more precise set of top terms, increase maxTermsPerTopic.
-   *
    * @param maxTermsPerTopic  Maximum number of terms to collect for each topic.
    * @return  Array over topics.  Each topic is represented as a pair of matching arrays:
    *          (term indices, term weights in topic).
@@ -519,9 +515,6 @@ class DistributedLDAModel private[clustering] (
   /**
    * Return the top documents for each topic
    *
-   * This is approximate; it may not return exactly the top-weighted documents for each topic.
-   * To get a more precise set of top documents, increase maxDocumentsPerTopic.
-   *
    * @param maxDocumentsPerTopic  Maximum number of documents to collect for each topic.
    * @return  Array over topics.  Each element represent as a pair of matching arrays:
    *          (IDs for the documents, weights of the topic in these documents).