CLEANUP: server: fix update_status() function comment

srv_update_status() function comment says that the function "is designed
to be called asynchronously".

While this used to be true back then with 64cc49cf
("MAJOR: servers: propagate server status changes asynchronously.")

This is not true anymore since 3ff577e ("MAJOR: server: make server state changes
synchronous again")

Fixing the comment in order to better reflect current behavior.
diff --git a/src/server.c b/src/server.c
index add9d77..1247537 100644
--- a/src/server.c
+++ b/src/server.c
@@ -5270,8 +5270,7 @@
 }
 
 /*
- * This function applies server's status changes, it is
- * is designed to be called asynchronously.
+ * This function applies server's status changes.
  *
  * Must be called with the server lock held. This may also be called at init
  * time as the result of parsing the state file, in which case no lock will be