[EXAMPLES] Fix a typo in NAV panel

We have several examples...
diff --git a/src/site/site.xml b/src/site/site.xml
index 7549182..b87dec5 100644
--- a/src/site/site.xml
+++ b/src/site/site.xml
@@ -68,7 +68,7 @@
         <menu name="MIME4J">
             <item name="Overview" href="/index.html"/>
             <item name="Status" href="/status.html"/>
-            <item name="Example" href="/samples.html"/>
+            <item name="Examples" href="/samples.html"/>
             <item name="Usage" href="/usage.html"/>
             <item name="Mailing List" href="http://james.apache.org/mail.html#Mime4j" />
             <item name="Javadoc" href="/apidocs/index.html" />