Fix return size described for XxHash64.TryHash

Author: bartonjs

xml/System.IO.Hashing/XxHash64.xml

@@ -365,7 +365,7 @@ The XxHash64 algorithm supports an optional seed value.
         <param name="seed">The seed value for this hash computation. The default is zero.</param>
         <summary>Attempts to compute the XxHash64 hash of the provided data into the provided destination.</summary>
         <returns>
-          <see langword="true" /> if <paramref name="destination" /> is long enough to receive the computed hash value (4 bytes); otherwise, <see langword="false" />.</returns>
+          <see langword="true" /> if <paramref name="destination" /> is long enough to receive the computed hash value (8 bytes); otherwise, <see langword="false" />.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>