Fixed a comment.

src/event/ngx_event_timer.c

diff --git a/src/event/ngx_event_timer.c b/src/event/ngx_event_timer.c
index 20e52f4..698b88f 100644
--- a/src/event/ngx_event_timer.c
+++ b/src/event/ngx_event_timer.c
@@ -67,7 +67,7 @@
 
         node = ngx_rbtree_min(root, sentinel);
 
-        /* node->key > ngx_current_time */
+        /* node->key > ngx_current_msec */
 
         if ((ngx_msec_int_t) (node->key - ngx_current_msec) > 0) {
             return;