[doc][mllib] Fix typo of the page title in Isotonic regression documents

* Fix the page title in Isotonic regression documents (Naive Bayes -> Isotonic regression)
* Add a newline character at the end of the file

Author: dobashim <dobashim@oss.nttdata.co.jp>

Closes apache#5581 from dobashim/master and squashes the following commits:

d54a041 [dobashim] Fix typo of the page title in Isotonic regression documents

docs/mllib-isotonic-regression.md

@@ -1,6 +1,6 @@
 ---
 layout: global
-title: Naive Bayes - MLlib
+title: Isotonic regression - MLlib
 displayTitle: <a href="mllib-guide.html">MLlib</a> - Regression
 ---
 
@@ -152,4 +152,4 @@ Double meanSquaredError = new JavaDoubleRDD(predictionAndLabel.map(
 System.out.println("Mean Squared Error = " + meanSquaredError);
 {% endhighlight %}
 </div>
-</div>
+</div>