Fix compile error in coreclr/runtime/amd64/AllocFast.S

 on illumos with gcc 13.3 cross copmiler
 coreclr/runtime/amd64/AllocFast.S: Assembler messages:
  coreclr/runtime/amd64/AllocFast.S:237: Error: missing ')'

Author: gwr

src/coreclr/runtime/amd64/AllocFast.S

@@ -234,7 +234,7 @@ LEAF_ENTRY RhpNewPtrArrayFast, _TEXT
 
         // Delegate overflow handling to the generic helper conservatively
 
-        cmp         rsi, (0x40000000 / 8) // sizeof(void*)
+        cmp         rsi, 0x40000000 / 8        // 0x40000000 / sizeof(void*)
         jae         C_FUNC(RhpNewArrayFast)
 
         // In this case we know the element size is sizeof(void *), or 8 for x64