[gnome-latex] Document: fix compil warning

[Sébastien Wilmet <swilmet src gnome org>]

commit 6fc729db78e2f0aad2ffc194a5eb5bc45105d6c2
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Apr 19 13:41:19 2020 +0200

    Document: fix compil warning
    
    There is now tepl_buffer_get_metadata().

 src/document.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/document.vala b/src/document.vala
index 6fd564e..1795178 100644
--- a/src/document.vala
+++ b/src/document.vala
@@ -544,7 +544,7 @@ public class Document : Tepl.Buffer
         save_metadata ();
     }
 
-    public string? get_metadata (string key)
+    public new string? get_metadata (string key)
     {
         return_val_if_fail (_metadata_info != null, null);