8311179: Generational ZGC: gc/z/TestSmallHeap.java failed with OutOfMemoryError

Reviewed-by: aboldtch, tschatzl
Backport-of: 28fd7a1

Author: stefank

test/hotspot/jtreg/gc/z/TestSmallHeap.java

@@ -28,7 +28,7 @@
  * @requires vm.gc.ZGenerational
  * @summary Test ZGC with small heaps
  * @library / /test/lib
- * @run driver gc.z.TestSmallHeap 8M 16M 32M 64M 128M 256M 512M 1024M
+ * @run driver gc.z.TestSmallHeap 16M 32M 64M 128M 256M 512M 1024M
  */
 
 import jdk.test.lib.process.ProcessTools;