Chunk: fixed hasChanged being set on fastDeserialize() chunks (caused by 2bb497b716)

this caused some performance issues and silent bugs with the generator, notably that the generator would always think all chunks had been changed, causing them to be re-set back into the world 9 times.

src/pocketmine/level/format/Chunk.php

@@ -929,6 +929,7 @@ class Chunk{
 		$chunk->setGenerated($terrainGenerated);
 		$chunk->setPopulated($terrainPopulated);
 		$chunk->setLightPopulated($lightPopulated);
+		$chunk->setChanged(false);
 
 		return $chunk;
 	}