[SPARK-50614][SQL] Fix shredding debug message

### What changes were proposed in this pull request?

A debug message added in apache#49234 was missing a brace. As a result, the message was printing the non-pretty string representation of the struct, followed by the string `.prettyJson}`. This PR fixes it.

### Why are the changes needed?

Cleaner debug messages.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Manually verified in spark-shell that the message looks wrong without the change, and correct with the change.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#49345 from cashmand/fix_debug_msg.

Authored-by: cashmand <david.cashman@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetWriteSupport.scala

@@ -158,7 +158,7 @@ class ParquetWriteSupport extends WriteSupport[InternalRow] with Logging {
         s"""Initialized Parquet WriteSupport with Catalyst schema:
            |${schema.prettyJson}
            |and shredding schema:
-           |$shreddedSchema.prettyJson}
+           |${shreddedSchema.prettyJson}
            |and corresponding Parquet message type:
            |$messageType
          """.stripMargin)