[MINOR][SQL] Remove unused variable in NewInstance.constructor

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

This PR removes one unused variable in `NewInstance.constructor`.

### Why are the changes needed?

This looks like a variable for debugging at the initial commit of SPARK-23584 .
- 1b08c43#diff-2a36e31684505fd22e2d12a864ce89fd350656d716a3f2d7789d2cdbe38e15fbR461

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

No.

### How was this patch tested?

Pass the CIs.

Closes #31838 from dongjoon-hyun/minor-object.

Authored-by: Dongjoon Hyun <dhyun@apple.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
(cherry picked from commit 0a70dff)
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala

@@ -456,7 +456,6 @@ case class NewInstance(
     }
     outerPointer.map { p =>
       val outerObj = p()
-      val d = outerObj.getClass +: paramTypes
       val c = getConstructor(outerObj.getClass +: paramTypes)
       (args: Seq[AnyRef]) => {
         c(outerObj +: args)