Minor cosmetic cleanups to imports etc

Please see https://hub.spigotmc.org/stash/projects/SPIGOT/repos/bukkit/pull-requests/389/overview

By: Parker Hawke <hawkeboyz2@hotmail.com>

paper-api/src/main/java/org/bukkit/block/data/type/Slab.java

@@ -1,13 +1,12 @@
 package org.bukkit.block.data.type;
 
-import org.bukkit.block.data.BlockData;
 import org.bukkit.block.data.Waterlogged;
 
 /**
  * 'type' represents what state the slab is in - either top, bottom, or a double
  * slab occupying the full block.
  */
-public interface Slab extends BlockData, Waterlogged {
+public interface Slab extends Waterlogged {
 
     /**
      * Gets the value of the 'type' property.