[SPARK-17213][SQL][FOLLOWUP] Re-enable Parquet filter tests for binary and string

## What changes were proposed in this pull request?

This PR proposes to enable the tests for Parquet filter pushdown with binary and string.

This was disabled in apache#16106 due to Parquet's issue but it is now revived in apache#16791 after upgrading Parquet to 1.8.2.

## How was this patch tested?

Manually tested `ParquetFilterSuite` via IDE.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes apache#16817 from HyukjinKwon/SPARK-17213.

Author: HyukjinKwon

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala

@@ -229,8 +229,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
     }
   }
 
-  // See SPARK-17213: https://issues.apache.org/jira/browse/SPARK-17213
-  ignore("filter pushdown - string") {
+  test("filter pushdown - string") {
     withParquetDataFrame((1 to 4).map(i => Tuple1(i.toString))) { implicit df =>
       checkFilterPredicate('_1.isNull, classOf[Eq[_]], Seq.empty[Row])
       checkFilterPredicate(
@@ -258,8 +257,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
     }
   }
 
-  // See SPARK-17213: https://issues.apache.org/jira/browse/SPARK-17213
-  ignore("filter pushdown - binary") {
+  test("filter pushdown - binary") {
     implicit class IntToBinary(int: Int) {
       def b: Array[Byte] = int.toString.getBytes(StandardCharsets.UTF_8)
     }