[SPARK-16553][DOCS] Fix SQL example file name in docs

## What changes were proposed in this pull request?

Fixes a typo in the sql programming guide

## How was this patch tested?

Building docs locally

(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #14208 from shivaram/spark-sql-doc-fix.

docs/sql-programming-guide.md

@@ -249,7 +249,7 @@ In addition to simple column references and expressions, DataFrames also have a
 <div data-lang="scala"  markdown="1">
 The `sql` function on a `SparkSession` enables applications to run SQL queries programmatically and returns the result as a `DataFrame`.
 
-{% include_example run_sql scala/org/apache/spark/examples/sql/SparkSQLExample.scala %}
+{% include_example run_sql scala/org/apache/spark/examples/sql/SparkSqlExample.scala %}
 </div>
 
 <div data-lang="java" markdown="1">