Fix Javadoc generation on Java 11

Author: garydgregory

src/main/javadoc/overview.html

@@ -85,10 +85,12 @@ <h1>Main features</h1>
   </tr>
   <tr>
     <td>
-      {@link org.apache.commons.collections4.Closure}<br />
-      {@link org.apache.commons.collections4.Predicate}<br />
-      {@link org.apache.commons.collections4.Transformer}<br />
-      {@link org.apache.commons.collections4.Factory}<br />
+      <ul>
+        <li>{@link org.apache.commons.collections4.Closure}</li>
+        <li>{@link org.apache.commons.collections4.Predicate}</li>
+        <li>{@link org.apache.commons.collections4.Transformer}</li>
+        <li>{@link org.apache.commons.collections4.Factory}</li>
+      </ul>
     </td>
     <td>
       A group of <i>functor</i> interfaces that provide plugin behavior to various