Fix bug in JavaRegressionMetricsExample.

the original code cant visit the last element of the"parts" array.
so the v[v.length–1] always equals 0

## What changes were proposed in this pull request?
change the recycle range from (1 to parts.length-1) to (1 to parts.length)

## How was this patch tested?

debug it in eclipse (´〜｀*) zzz.

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

Author: junzhi lu <452756565@qq.com>

Closes #18237 from masterwugui/patch-1.

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

@@ -40,7 +40,7 @@ public class JavaRegressionMetricsExample {
     JavaRDD<LabeledPoint> parsedData = data.map(line -> {
       String[] parts = line.split(" ");
       double[] v = new double[parts.length - 1];
-      for (int i = 1; i < parts.length - 1; i++) {
+      for (int i = 1; i < parts.length; i++) {
         v[i - 1] = Double.parseDouble(parts[i].split(":")[1]);
       }
       return new LabeledPoint(Double.parseDouble(parts[0]), Vectors.dense(v));