[gnome-boxes] copyright: Update link to file format spec

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 48b2848e3f5207939be4f3da3dc34c42ca11c0e1
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Thu Feb 5 17:57:52 2015 +0000

    copyright: Update link to file format spec
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743361

 copyright |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/copyright b/copyright
index b42e95c..8400d5d 100644
--- a/copyright
+++ b/copyright
@@ -1,4 +1,4 @@
-Format: http://www.debian.org/doc/copyright-format/1.0
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
 Upstream-Name: GNOME Boxes
 
 Files: *