[libgnome-keyring] Fix vapi build with vala 0.42

[Rico Tzschichholz <ricotz src gnome org>]

commit 3766bcc482f9e02fb5f9c183e814833ad1fbf08a
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Tue Jan 8 12:19:36 2019 +0100

    Fix vapi build with vala 0.42

 library/GnomeKeyring-1.0.metadata | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/library/GnomeKeyring-1.0.metadata b/library/GnomeKeyring-1.0.metadata
index 04662fb..d8451b9 100644
--- a/library/GnomeKeyring-1.0.metadata
+++ b/library/GnomeKeyring-1.0.metadata
@@ -54,7 +54,7 @@ set_info skip=false
 set_network_password skip=false
 store_password skip=false
 store_password_sync skip=false
-unlock skip=false
+@unlock skip=false
 
 find_items*.callback type_arguments="GnomeKeyring.Found"
 find_network_password*.callback type_arguments="GnomeKeyring.NetworkPasswordData"