pass --add-opens to Spark PVR test JVM on Java 21 (#39278)

Author: aIbrahiim

.github/trigger_files/beam_PostCommit_Java_PVR_Spark3_Streaming.json

@@ -1,4 +1,4 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 5
+  "modification": 6
 }

runners/spark/job-server/spark_job_server.gradle

@@ -280,6 +280,13 @@ def sparkJobServerJvmArgs() {
   return []
 }
 
+// TestPortableRunner starts SparkJobServerDriver in-process in the test JVM.
+['validatesPortableRunnerDocker', 'validatesPortableRunnerBatch', 'validatesPortableRunnerStreaming'].each { taskName ->
+  tasks.named(taskName) {
+    jvmArgs += sparkJobServerJvmArgs()
+  }
+}
+
 def setupTask = project.tasks.register("sparkJobServerSetup", Exec) {
   dependsOn shadowJar
   def pythonDir = project.project(":sdks:python").projectDir