Mention DateTimeKind unspecified in DateOnly.ToDateTime (#10285)

* Mention DateTimeKind unspecified in DateOnly.ToDateTime

* Update xml/System/DateOnly.xml

Co-authored-by: Genevieve Warren <[email protected]>

---------

Co-authored-by: Genevieve Warren <[email protected]>

Author: rzikm

xml/System/DateOnly.xml

@@ -1431,7 +1431,15 @@
         <param name="time">The time of the day.</param>
         <summary>Returns a <see cref="T:System.DateTime" /> that is set to the date of this <see cref="T:System.DateOnly" /> instance and the time of specified input time.</summary>
         <returns>The <see cref="T:System.DateTime" /> instance composed of the date of the current <see cref="T:System.DateOnly" /> instance and the time specified by the input time.</returns>
-        <remarks>To be added.</remarks>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+
+## Remarks
+
+The <xref:System.DateTime.Kind> property of the resulting <xref:System.DateTime> is initialized to <xref:System.DateTimeKind.Unspecified?displayProperty=nameWithType>.
+            
+]]></format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="ToDateTime">