Error in docs Vector<256>.WithUpper(..) (dotnet#4610)

Author: dmitry-valyukov

xml/System.Runtime.Intrinsics/Vector256.xml

@@ -2753,7 +2753,7 @@ On x86, this method corresponds to __m256i _mm256_setr_epi8
         <typeparam name="T">The type of the input vector.</typeparam>
         <param name="vector">The vector to get the lower 128-bits from.</param>
         <param name="value">The value of the upper 128-bits as a <see cref="T:System.Runtime.Intrinsics.Vector128`1" />.</param>
-        <summary>Creates a new <see cref="T:System.Runtime.Intrinsics.Vector256`1" /> with the upper 128-bits set to the specified value and the upper 128-bits set to the same value as that in the given vector.</summary>
+        <summary>Creates a new <see cref="T:System.Runtime.Intrinsics.Vector256`1" /> with the upper 128-bits set to the specified value and the lower 128-bits set to the same value as that in the given vector.</summary>
         <returns>A new <see cref="T:System.Runtime.Intrinsics.Vector256`1" /> with the upper 128-bits set to the specified value and the upper 128-bits set to the same value as that in <paramref name="vector" />.</returns>
         <remarks>To be added.</remarks>
         <exception cref="T:System.NotSupportedException">The type of <paramref name="vector" /> (<typeparamref name="T" />) is not supported.</exception>