Updated Page Titled for better links (#3824)

1. updated the "document collection" Understanding link to say WCAG 2.2
instead of 2.1.
2. updated the quoted page title for the Introduction to WCAG page.
3. linked to Introduction to WCAG page.

Note: I don't understand the references to the appendices on the WCAG
homepage. What do they have to do with page titles?

---------

Co-authored-by: Patrick H. Lauke <redux@splintered.co.uk>

understanding/20/page-titled.html

@@ -98,13 +98,10 @@ <h2>Examples of Page Titled</h2>
                that it will be displayed in the title bar of the user agent.</dd>
          <dt>A document collection</dt>
          <dd>
-            <p>The title of <a href="./">Understanding WCAG 2.1 </a>
-               is "Understanding WCAG 2.1."</p>
+            <p>The title of <a href="./">Understanding WCAG 2.2</a> is "Understanding WCAG 2.2".</p>
             <ul>
-               <li>The introduction page has the title "Introduction to Understanding WCAG 2.0."</li>
-               <li>Major sections of the document are pages titled "Understanding Guideline X" and "Understanding
-                  Success Criterion X." 
-               </li>
+               <li>The <a href="../Understanding/intro">Introduction to Understanding WCAG</a> page has the title "Introduction to Understanding WCAG".</li>
+               <li>Major sections of the document collection are pages titled "Understanding Guideline X" and "Understanding Success Criterion X."</li>
                <li>Appendix A has the title "Glossary."</li>
                <li>Appendix B has the title "Acknowledgements."</li>
                <li>Appendix C has the title "References."</li>