fix: add tracking issue link to IgnoreCometNativeScan for StringPredicate test

Address review feedback by including issue #3321 link in the
IgnoreCometNativeScan reason string so the gap can be tracked.

Author: andygrove

dev/diffs/3.4.3.diff

@@ -2003,7 +2003,7 @@ index 07e2849ce6f..3e73645b638 100644
        ParquetOutputFormat.WRITER_VERSION -> ParquetProperties.WriterVersion.PARQUET_2_0.toString
      )
 diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala
-index 104b4e416cd..0897e4f3776 100644
+index 104b4e416cd..5ff142320cd 100644
 --- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala
 +++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala
 @@ -38,6 +38,7 @@ import org.apache.parquet.schema.MessageType
@@ -2069,7 +2069,7 @@ index 104b4e416cd..0897e4f3776 100644
 
 -  test("filter pushdown - StringPredicate") {
 +  test("filter pushdown - StringPredicate",
-+    IgnoreCometNativeScan("cannot be pushed down")) {
++    IgnoreCometNativeScan("https://github.com/apache/datafusion-comet/issues/3321")) {
      import testImplicits._
      // keep() should take effect on StartsWith/EndsWith/Contains
      Seq(