Re-enable "transpile complex regex 2" scala test (#6027)

Signed-off-by: Anthony Chang <antchang@nvidia.com>

tests/src/test/scala/com/nvidia/spark/rapids/RegularExpressionTranspilerSuite.scala

@@ -382,13 +382,10 @@ class RegularExpressionTranspilerSuite extends FunSuite with Arm {
     assert(transpiled === expected)
   }
 
-  // this was a test for transpiling but we did not ever try to run the
-  // resulting regex to see if it produced valid results
-  // see https://github.com/NVIDIA/spark-rapids/issues/5656
-  ignore("transpile complex regex 2") {
+  test("transpile complex regex 2") {
     val TIMESTAMP_TRUNCATE_REGEX = "^([0-9]{4}-[0-9]{2}-[0-9]{2} " +
       "[0-9]{2}:[0-9]{2}:[0-9]{2})" +
-      "(.[1-9]*(?:0)?[1-9]+)?(.0*[1-9]+)?(?:.0*)?\\z"
+      "(.[1-9]*(?:0)?[1-9]+)?(.0*[1-9]+)?(?:.0*)?.\\z"
 
     // input and output should be identical except for `.` being replaced 
     // with `[^\n\r\u0085\u2028\u2029]` and `\z` being replaced with `$`