Add mappings for world chunk ticking (#509)

mappings/net/minecraft/server/world/ServerChunkManager.mapping

@@ -40,4 +40,4 @@ CLASS ut net/minecraft/server/world/ServerChunkManager
 	METHOD g getLoadedChunkCount ()I
 	METHOD h getPersistentStateManager ()Lcjq;
 	METHOD k update ()Z
-	METHOD l doMobSpawning ()V
+	METHOD l tickChunks ()V

mappings/net/minecraft/server/world/ServerWorld.mapping

@@ -30,6 +30,9 @@ CLASS uv net/minecraft/server/world/ServerWorld
 	METHOD a addLightning (Lapp;)V
 	METHOD a init (Lbdj;)V
 		ARG 1 levelInfo
+	METHOD a tickChunk (Lbte;I)V
+		ARG 1 chunk
+		ARG 2 randomTickSpeed
 	METHOD a getEntity (Ljava/util/UUID;)Lahm;
 	METHOD a save (Lzi;ZZ)V
 		ARG 1 progressListener