test runtime/Unsafe/InternalErrorTest.java timeout on linux-riscv64 platform

This issue happens after JDK-8320886: Unsafe_SetMemory0 is not guarded which added testing Unsafe.setMemory, trying to access next page after truncation.

The test pass if changing NUM_TESTS to 3, like:

diff --git a/test/hotspot/jtreg/runtime/Unsafe/InternalErrorTest.java b/test/hotspot/jtreg/runtime/Unsafe/InternalErrorTest.java
index fcf48a7a2d7..49e83c88db6 100644
--- a/test/hotspot/jtreg/runtime/Unsafe/InternalErrorTest.java
+++ b/test/hotspot/jtreg/runtime/Unsafe/InternalErrorTest.java
@@ -61,7 +61,7 @@ public class InternalErrorTest {
     private static final String failureMsg1 = "InternalError not thrown";
     private static final String failureMsg2 = "Wrong InternalError: ";

- private static final int NUM_TESTS = 4;
+ private static final int NUM_TESTS = 3;

     public static void main(String[] args) throws Throwable {
         Unsafe unsafe = Unsafe.getUnsafe();