Replace usage of -noclassgc with -Xnoclassgc in test/jdk/java/lang/management/MemoryMXBean/LowMemoryTest2.java

The "-noclassgc" is an undocumented java launcher option, which the java launcher internally converts to the HotSpot VM specific "-Xnoclassgc" before passing it to the JVM.

The test/jdk/java/lang/management/MemoryMXBean/LowMemoryTest2.java should instead use "-Xnoclassgc" which is specified in the java command specification https://docs.oracle.com/en/java/javase/22/docs/specs/man/java.html#extra-options-for-java as being specific to Hotspot JVM.