[SPARK-17347][SQL][EXAMPLES] Encoder in Dataset example has incorrect type

## What changes were proposed in this pull request?

We propose to fix the Encoder type in the Dataset example

## How was this patch tested?

The PR will be tested with the current unit test cases

Author: CodingCat <zhunansjtu@gmail.com>

Closes #14901 from CodingCat/SPARK-17347.

examples/src/main/scala/org/apache/spark/examples/sql/SparkSQLExample.scala

@@ -203,7 +203,7 @@ object SparkSQLExample {
     // No pre-defined encoders for Dataset[Map[K,V]], define explicitly
     implicit val mapEncoder = org.apache.spark.sql.Encoders.kryo[Map[String, Any]]
     // Primitive types and case classes can be also defined as
-    implicit val stringIntMapEncoder: Encoder[Map[String, Int]] = ExpressionEncoder()
+    // implicit val stringIntMapEncoder: Encoder[Map[String, Any]] = ExpressionEncoder()
 
     // row.getValuesMap[T] retrieves multiple columns at once into a Map[String, T]
     teenagersDF.map(teenager => teenager.getValuesMap[Any](List("name", "age"))).collect()