C#: Removed invalid strings from example (#2266)

C#'s example page contained some invalid strings.

examples/prism-csharp.html

@@ -5,12 +5,9 @@ <h2>Comments</h2>
 
 <h2>Strings</h2>
 <pre><code>"foo \"bar\" baz"
-'foo \'bar\' baz'
 @"Verbatim strings"
 @"Luis: ""Patrick, where did you get that overnight bag?""
     Patrick: ""Jean Paul Gaultier.""";
-@'Luis: ''Patrick, where did you get that overnight bag?''
-    Patrick: ''Jean Paul Gaultier.''';
 </code></pre>
 
 <h2>Full example</h2>
@@ -57,4 +54,4 @@ <h2>Full example</h2>
   DialogResult dialogResult = form.ShowDialog();
   value = textBox.Text;
   return dialogResult;
-}</code></pre>
+}</code></pre>