This rule flags the use of the javax.management.remote.rmi.RMIIIOPServerImpl class which was removed in Java SE 21.
The JMX Remote API (javax.management.remote.rmi) was changed in Java 8 (and JSR-160 MR3) to make the IIOP transport optional (JDK-8001048). This was to allow for Compact Profiles and in preparation for moving the Java Platform to modules.
Support for the IIOP transport was removed from the JMX Remote API in Java 9.
In Java 9 the class was deprecated and "degraded". Its constructor was specified to throw UOE(java.lang.UnsupportedOperationException). In Java SE 21, this class is removed.
For more information see JSR-160 MR3. JDK-8001048. JDK-8307244. JDK-8307329.