[MINOR][SQL] Fix exception message to print string-array correctly.

## What changes were proposed in this pull request?

This PR is a simple fix for an exception message to print `string[]` content correctly.
```java
String[] colPath = requestedSchema.getPaths().get(i);
...
-          throw new IOException("Required column is missing in data file. Col: " + colPath);
+          throw new IOException("Required column is missing in data file. Col: " + Arrays.toString(colPath));
```

## How was this patch tested?

Manual.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12041 from dongjoon-hyun/fix_exception_message_with_string_array.

sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedParquetRecordReader.java

@@ -18,6 +18,7 @@
 package org.apache.spark.sql.execution.datasources.parquet;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.List;
 
 import org.apache.hadoop.mapreduce.InputSplit;
@@ -269,7 +270,8 @@ public class VectorizedParquetRecordReader extends SpecificParquetRecordReaderBa
       } else {
         if (requestedSchema.getColumns().get(i).getMaxDefinitionLevel() == 0) {
           // Column is missing in data but the required data is non-nullable. This file is invalid.
-          throw new IOException("Required column is missing in data file. Col: " + colPath);
+          throw new IOException("Required column is missing in data file. Col: " +
+            Arrays.toString(colPath));
         }
         missingColumns[i] = true;
       }