[MINOR][SQL] remove Redundant semicolons

## What changes were proposed in this pull request?

remove Redundant semicolons in SortMergeJoinExec， thanks.

## How was this patch tested?

N/A

Closes #22695 from heary-cao/RedundantSemicolons.

Authored-by: caoxuewen <cao.xuewen@zte.com.cn>
Signed-off-by: Sean Owen <sean.owen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala

@@ -494,7 +494,7 @@ case class SortMergeJoinExec(
          |        $leftRow = null;
          |      } else {
          |        $matches.add((UnsafeRow) $rightRow);
-         |        $rightRow = null;;
+         |        $rightRow = null;
          |      }
          |    } while ($leftRow != null);
          |  }