TimeOnly - Fix constructor summary (dotnet#8665)

Author: wootcorp

xml/System/TimeOnly.xml

@@ -180,7 +180,7 @@
         <param name="second">The seconds (0 through 59).</param>
         <param name="millisecond">The millisecond (0 through 999).</param>
         <param name="microsecond">The microsecond (0 through 999).</param>
-        <summary>Initializes a new instance of the <see cref="T:System.TimeOnly" /> structure to the specified hour, minute, second, and millisecond.</summary>
+        <summary>Initializes a new instance of the <see cref="T:System.TimeOnly" /> structure to the specified hour, minute, second, millisecond, and microsecond.</summary>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>