Remove test

Author: benaadams

src/System.IO.Pipelines/ReadableBuffer.cs

@@ -55,11 +55,6 @@ public struct ReadableBuffer : ISequence<ReadOnlyMemory<byte>>
 
         internal ReadableBuffer(ReadCursor start, ReadCursor end)
         {
-            if (!end.IsEnd && !end.GreaterOrEqual(start))
-            {
-                ThrowHelper.ThrowArgumentException_ReadableBufferCtor();
-            }
-
             _start = start;
             _end = end;
             _length = -1;