CLEANUP: lua: remove the unused hlua_sleep memory pool

Commit d44731f ("MEDIUM: lua: change the sleep function core") removed
the use for this pool but forgot to remove the pool which is still
created.
diff --git a/src/hlua.c b/src/hlua.c
index 1e1c114..c6dcd89 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -54,7 +54,6 @@
  * struct are used to store each requiered signal between two tasks.
  */
 struct pool_head *pool2_hlua_com;
-struct pool_head *pool2_hlua_sleep;
 
 /* Used for Socket connection. */
 static struct proxy socket_proxy;
@@ -4619,9 +4618,6 @@
 	/* Initialise com signals pool session. */
 	pool2_hlua_com = create_pool("hlua_com", sizeof(struct hlua_com), MEM_F_SHARED);
 
-	/* Initialise sleep pool. */
-	pool2_hlua_sleep = create_pool("hlua_sleep", sizeof(struct hlua_sleep), MEM_F_SHARED);
-
 	/* Register configuration keywords. */
 	cfg_register_keywords(&cfg_kws);