C150427: Fixing CDATA formatting (#3653)

Localization team has reported source content issue that causes localized version to have broken/different format compared to en-us version.
Description: the Markdown CDATA content is incorrectly formatted in source files, moreover it is breaking the target publishing builds since the content inside those tags are being processed as XML tag instead of Markdown content.

Author: v-maudel

xml/System.IO/StringReader.xml

@@ -735,8 +735,7 @@ This implementation of `Close` calls the <xref:System.IO.StringReader.Dispose%2A
         <summary>Asynchronously reads all the characters from the input string starting at the current position and advances the current position to the end of the input string.</summary>
         <returns>A task representing the asynchronous read operation. The value of the <paramref name="TResult" /> parameter contains the total number of characters read into the buffer.</returns>
         <remarks>
-          <format type="text/markdown">
-  <![CDATA[
+          <format type="text/markdown"><![CDATA[
 
 ## Remarks