Fix some javadoc warnings

Also remove a couple old/broken deprecated methods

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

paper-api/src/main/java/org/bukkit/entity/AreaEffectCloud.java

@@ -138,6 +138,7 @@ public interface AreaEffectCloud extends Entity {
     /**
      * Sets the particle which this cloud will be composed of
      *
+     * @param <T> type of particle data (see {@link Particle#getDataType()}
      * @param particle the new particle type
      * @param data the data to use for the particle or null,
      *             the type of this depends on {@link Particle#getDataType()}