Update to Minecraft 1.15

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

paper-server/nms-patches/ItemLeash.patch

@@ -20,7 +20,7 @@
 +
 +                    if (event.isCancelled()) {
 +                        entityleash.die();
-+                        return false;
++                        return EnumInteractionResult.PASS;
 +                    }
 +                    // CraftBukkit end
 +                }