[SPARK-14295][MLLIB][HOTFIX] Fixes Scala 2.10 compilation failure

## What changes were proposed in this pull request?

Fixes a compilation failure introduced in PR #12088 under Scala 2.10.

## How was this patch tested?

Compilation.

Author: Cheng Lian <lian@databricks.com>

Closes #12107 from liancheng/spark-14295-hotfix.

mllib/src/main/scala/org/apache/spark/mllib/util/MLUtils.scala

@@ -120,7 +120,7 @@ object MLUtils {
       i += 1
     }
 
-    (label, indices, values)
+    (label, indices.toArray, values.toArray)
   }
 
   /**