server: A spelling and slight rewording fix in a comment.

server/async.c

@@ -50,7 +50,7 @@ struct async
     struct iosb         *iosb;            /* I/O status block */
     obj_handle_t         wait_handle;     /* pre-allocated wait handle */
     unsigned int         signaled :1;
-    unsigned int         pending :1;      /* request is succesfully queued, but pending */
+    unsigned int         pending :1;      /* request successfully queued, but pending */
     unsigned int         direct_result :1;/* a flag if we're passing result directly from request instead of APC  */
     struct completion   *completion;      /* completion associated with fd */
     apc_param_t          comp_key;        /* completion key associated with fd */