Remove redundant cross_modify_fence()

Remove cross_modify_fence() from ~ThreadBlockInVM(), ~ThreadBlockInVMWithDeadlockCheck() and java_suspend_self_with_safepoint_check().
These fences were added before each JavaThread had to disarm itself (JDK-8230594). After a safepoint/handshake each JavaThread will always call SafepointMechanism::process_if_requested_slow() when transitioning out of the safe state and will execute a cross_modify_fence().