Apply suggestions from code review

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

Author: tmds

xml/System.Runtime.InteropServices/RuntimeInformation.xml

@@ -245,6 +245,7 @@ The returned value is intended to represent the actual architecture of the under
       <Docs>
         <summary>Gets a string that describes the operating system on which the app is running.</summary>
         <value>An opaque string that describes the operating system on which the app is running.</value>
+        <remarks>
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
@@ -254,6 +255,7 @@ This property returns a string that describes the operating system for presentat
 It's not recommended to parse the string for information.
 
  ]]></format>
+    </remarks>
       </Docs>
     </Member>
     <Member MemberName="ProcessArchitecture">