Fix spawner API documentation

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/spawner/Spawner.java

@@ -10,6 +10,17 @@ import org.bukkit.entity.minecart.SpawnerMinecart;
  */
 public interface Spawner extends BaseSpawner {
 
+    /**
+     * {@inheritDoc}
+     * <br>
+     * If set to -1, the spawn delay will be reset to a random value between
+     * {@link #getMinSpawnDelay} and {@link #getMaxSpawnDelay()}.
+     *
+     * @param delay The delay.
+     */
+    @Override
+    public void setDelay(int delay);
+
     /**
      * The minimum spawn delay amount (in ticks).
      * <br>