git: openjdk/loom: fibers: Change HeapMonitorVMEventsTest to not enable preview when virtual threads are unused

[duke]

Changeset: 9b8e1b4f
Author:    Ron Pressler <ron.pressler at oracle.com>
Date:      2022-04-24 09:41:19 +0000
URL:       https://git.openjdk.java.net/loom/commit/9b8e1b4f073d6cb8b20d79bf548de37b916851b9

Change HeapMonitorVMEventsTest to not enable preview when virtual threads are unused

! test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorVMEventsTest.java