[Bleeding] Correct issues with MEGA_REDWOOD trees. Fixes BUKKIT-5568

In commit 6efeddfe57, TALL_REDWOOD was used instead of the proper TreeType
of MEGA_REDWOOD. Additionally, this fixes an issue in CraftWorld with an
improper boolean flag related to the generation of MEGA_REDWOOD trees.

By: GJ <gjmcferrin@gmail.com>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -393,7 +393,7 @@ public class CraftWorld implements World {
             gen = new WorldGenForestTree(true);
             break;
         case MEGA_REDWOOD:
-            gen = new WorldGenMegaTree(true, rand.nextBoolean());
+            gen = new WorldGenMegaTree(false, rand.nextBoolean());
             break;
         case TALL_BIRCH:
             gen = new WorldGenForest(true, true);