RFR(XXS) 8213275 ReplaceCriticalClasses.java fails with jdk.internal.vm.PostVMInitHook not found

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8213275
http://cr.openjdk.java.net/~iklam/jdk12/8213275-ReplaceCriticalClasses-missing-PostVMInitHook.v01/

Please review this simple fix. The jdk.internal.vm.PostVMInitHook class 
is not in the openjdk so it should be used in a test in the openjdk repo.

It isn't important to test for this particular class. When I wrote the 
test, I was just looking for a few classes that are loaded immediately 
after JVMTI has exited JVMTI_PHASE_PRIMORDIAL, and PostVMInitHook 
happened to be one of those classes.

Since we already test a few other classes such as java/util/Locale, the 
fix is simply to remove PostVMInitHook from the test.

Thanks
- Ioi