Tree View Examples: Update documentation of Accessibility Features

For issue #404, updated the statement in the accessibility features section
of each of the 4 tree view example pages.
Updated to document  the change to use of CSS pseudo-classes for focus and hover
made in commit  ba5cf02.

examples/treeview/treeview-1/treeview-1a.html

@@ -249,8 +249,7 @@ <h3 id="tree_label">
       <section>
         <h2>Accessibility Features</h2>
         <p>
-          To make the focus indicator easier to see, expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
-          To do this, focus, blur, mouseover, and mouseout events trigger application of classes to the <code>span</code> element that contains the visible label of the <code>treeitem</code>.
+          To make the focus indicator easier to see, nodes in the tree have a custom focus and hover styling created using CSS focus and hover pseudo-classes.
         </p>
       </section>
 

examples/treeview/treeview-1/treeview-1b.html

@@ -409,8 +409,7 @@ <h3 id="tree1">File Viewer</h3>
       <section>
         <h2>Accessibility Features</h2>
         <p>
-          To make the focus indicator easier to see, the expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
-          To do this, focus, blur, mouseover, and mouseout events trigger application of classes to the <code>span</code> element that contains the visible label of the <code>treeitem</code>.
+          To make the focus indicator easier to see, nodes in the tree have a custom focus and hover styling created using CSS focus and hover pseudo-classes.
         </p>
       </section>
 

examples/treeview/treeview-2/treeview-2a.html

@@ -331,8 +331,7 @@ <h3 id="tree1">Foods</h3>
       <section>
         <h2>Accessibility Features</h2>
         <p>
-          To make the focus indicator easier to see, the expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
-          To do this, focus, blur, mouseover, and mouseout events trigger application of classes to the <code>span</code> element that contains the visible label of the <code>treeitem</code>.
+          To make the focus indicator easier to see, nodes in the tree have a custom focus and hover styling created using CSS focus and hover pseudo-classes.
         </p>
       </section>
 

examples/treeview/treeview-2/treeview-2b.html

@@ -463,8 +463,7 @@ <h3 id="tree1">Foods</h3>
       <section>
         <h2>Accessibility Features</h2>
         <p>
-          To make the focus indicator easier to see, the expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
-          To do this, focus, blur, mouseover, and mouseout events trigger application of classes to the <code>span</code> element that contains the visible label of the <code>treeitem</code>.
+          To make the focus indicator easier to see, nodes in the tree have a custom focus and hover styling created using CSS focus and hover pseudo-classes.
         </p>
       </section>