[MNG-6847] Use diamond operator

Use this link to re-run the recipe: https://app.moderne.io/recipes/builder/SEvWu02zw?organizationId=QXBhY2hlIE1hdmVu

Co-authored-by: Moderne <team@moderne.io>

build-plugin/src/main/java/org/mvndaemon/mvnd/plugin/doc/DocMojo.java

@@ -125,7 +125,7 @@ public class DocMojo extends AbstractMojo {
         @Override
         public synchronized Enumeration<Object> keys() {
             final Iterator<Object> it = new TreeSet<>(keySet()).iterator();
-            return new Enumeration<Object>() {
+            return new Enumeration<>() {
                 public boolean hasMoreElements() {
                     return it.hasNext();
                 }