Replace <code>…</code> with {@code …}

core/src/main/java/hudson/PluginManager.java

@@ -159,7 +159,7 @@ import static java.util.logging.Level.*;
  *
  * <p>
  * <b>Setting default Plugin Managers</b>. The default plugin manager in {@code Jenkins} can be replaced by defining a
- * System Property (<code>hudson.PluginManager.className</code>). See {@link #createDefault(Jenkins)}.
+ * System Property ({@code hudson.PluginManager.className}). See {@link #createDefault(Jenkins)}.
  * This className should be available on early startup, so it cannot come only from a library
  * (e.g. Jenkins module or Extra library dependency in the WAR file project).
  * Plugins cannot be used for such purpose.