Error in docs Vector<128>.WithUpper(..) (dotnet#4611)

* Error in docs Vector<128>.WithUpper(..)

* Apply suggestions from gewarren

Author: dmitry-valyukov

xml/System.Runtime.Intrinsics/Vector128.xml

@@ -2836,9 +2836,9 @@ On x86, this method corresponds to __m128i _mm_setr_epi8
       <Docs>
         <typeparam name="T">The type of the input vector.</typeparam>
         <param name="vector">The vector to get the lower 64-bits from.</param>
-        <param name="value">The value of the upper 64-bits as a <see cref="T:System.Runtime.Intrinsics.Vector64`1" />.</param>
-        <summary>Creates a new <see cref="T:System.Runtime.Intrinsics.Vector128`1" /> with the upper 64-bits set to the specified value and the upper 64-bits set to the same value as that in the given vector.</summary>
-        <returns>A new <see cref="T:System.Runtime.Intrinsics.Vector128`1" /> with the upper 64-bits set to the specified value and the upper 64-bits set to the same value as that in <paramref name="vector" />.</returns>
+        <param name="value">The upper 64-bits.</param>
+        <summary>Creates a new <see cref="T:System.Runtime.Intrinsics.Vector128`1" /> with the upper 64-bits set to the specified value and the lower 64-bits set to the same value as that in the given vector.</summary>
+        <returns>A new <see cref="T:System.Runtime.Intrinsics.Vector128`1" /> with the upper 64-bits set to the specified value and the lower 64-bits set to those 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>
       </Docs>