apply Levis suggestion: don't store Array.MaxLength as a const, as it…

… may change in the future

src/libraries/System.Formats.Nrbf/src/System/Formats/Nrbf/ArrayInfo.cs

@@ -16,7 +16,11 @@ namespace System.Formats.Nrbf;
 [DebuggerDisplay("{ArrayType}, rank={Rank}")]
 internal readonly struct ArrayInfo
 {
-    internal const int MaxArrayLength = 2147483591; // Array.MaxLength
+#if NET8_0_OR_GREATER
+    internal static int MaxArrayLength => Array.MaxLength; // dynamic lookup in case the value changes in a future runtime
+#else
+    internal const int MaxArrayLength = 2147483591; // hardcode legacy Array.MaxLength for downlevel runtimes
+#endif
 
     internal ArrayInfo(SerializationRecordId id, long totalElementsCount, BinaryArrayType arrayType = BinaryArrayType.Single, int rank = 1)
     {
@@ -47,7 +51,7 @@ internal static int ParseValidArrayLength(BinaryReader reader)
     {
         int length = reader.ReadInt32();
 
-        if (length is < 0 or > MaxArrayLength)
+        if (length < 0 || length > MaxArrayLength)
         {
             ThrowHelper.ThrowInvalidValue(length);
         }