[SPARK-24688][EXAMPLES] Modify the comments about LabeledPoint

## What changes were proposed in this pull request?

An RDD is created using LabeledPoint, but the comment is like #LabeledPoint(feature, label).
Although in the method ChiSquareTest.test, the second parameter is feature and the third parameter is label, it it better to write label in front of feature here because if an RDD is created using LabeldPoint, what we get are actually (label, feature) pairs.
Now it is changed as LabeledPoint(label, feature).

The comments in Scala and Java example have the same typos.

## How was this patch tested?

tested

https://issues.apache.org/jira/browse/SPARK-24688

Author: Weizhe Huang 492816239qq.com

Please review http://spark.apache.org/contributing.html before opening a pull request.

Closes #21665 from uzmijnlm/my_change.

Authored-by: Huangweizhe <[email protected]>
Signed-off-by: Sean Owen <[email protected]>

Author: huangweizhe123

examples/src/main/java/org/apache/spark/examples/mllib/JavaHypothesisTestingExample.java

@@ -67,7 +67,7 @@ public static void main(String[] args) {
       )
     );
 
-    // The contingency table is constructed from the raw (feature, label) pairs and used to conduct
+    // The contingency table is constructed from the raw (label, feature) pairs and used to conduct
     // the independence test. Returns an array containing the ChiSquaredTestResult for every feature
     // against the label.
     ChiSqTestResult[] featureTestResults = Statistics.chiSqTest(obs.rdd());

examples/src/main/python/mllib/hypothesis_testing_example.py

@@ -51,7 +51,7 @@
         [LabeledPoint(1.0, [1.0, 0.0, 3.0]),
          LabeledPoint(1.0, [1.0, 2.0, 0.0]),
          LabeledPoint(1.0, [-1.0, 0.0, -0.5])]
-    )  # LabeledPoint(feature, label)
+    )  # LabeledPoint(label, feature)
 
     # The contingency table is constructed from an RDD of LabeledPoint and used to conduct
     # the independence test. Returns an array containing the ChiSquaredTestResult for every feature

examples/src/main/scala/org/apache/spark/examples/mllib/HypothesisTestingExample.scala

@@ -61,9 +61,9 @@ object HypothesisTestingExample {
           LabeledPoint(-1.0, Vectors.dense(-1.0, 0.0, -0.5)
           )
         )
-      ) // (feature, label) pairs.
+      ) // (label, feature) pairs.
 
-    // The contingency table is constructed from the raw (feature, label) pairs and used to conduct
+    // The contingency table is constructed from the raw (label, feature) pairs and used to conduct
     // the independence test. Returns an array containing the ChiSquaredTestResult for every feature
     // against the label.
     val featureTestResults: Array[ChiSqTestResult] = Statistics.chiSqTest(obs)