[JDK21] Enable StructuredThreadDumpTest for OpenJ9 (#4659)

eclipse-openj9/openj9#17709 adds the required support to enable
StructuredThreadDumpTest.

Related issues which can be closed after the test is enabled:
- eclipse-openj9/openj9#17634
- eclipse-openj9/openj9#15278

Signed-off-by: Babneet Singh <sbabneet@ca.ibm.com>

openjdk/excludes/ProblemList_openjdk21-openj9.txt

@@ -431,7 +431,6 @@ java/util/Arrays/TimSortStackSize2.java https://github.com/eclipse-openj9/openj9
 java/util/BitSet/stream/BitSetStreamTest.java https://github.com/eclipse-openj9/openj9/issues/4720 linux-all
 java/util/concurrent/forkjoin/FJExceptionTableLeak.java https://github.com/eclipse-openj9/openj9/issues/3209 generic-all
 java/util/concurrent/locks/Lock/TimedAcquireLeak.java https://github.com/eclipse-openj9/openj9/issues/7125 macosx-all,linux-all,aix-all
-java/util/concurrent/StructuredTaskScope/StructuredThreadDumpTest.java https://github.com/eclipse-openj9/openj9/issues/17634 generic-all
 java/util/concurrent/TimeUnit/Basic.java https://github.com/adoptium/aqa-tests/issues/1665 windows-all
 java/util/logging/CheckZombieLockTest.java https://bugs.openjdk.java.net/browse/JDK-8148972 macosx-all,linux-all
 java/util/logging/LogManager/TestLoggerNames.java https://github.com/eclipse-openj9/openj9/issues/4561 generic-all