[shotwell] COPYING: Update 404 link for gnome-icon-theme

[Andre Klapper <aklapper src gnome org>]

commit 7eaa10cf59244cf70a8ecf4d00acafeb60ff02e4
Author: Andre Klapper <a9016009 gmx de>
Date:   Sat Apr 25 14:06:20 2020 +0200

    COPYING: Update 404 link for gnome-icon-theme

 COPYING | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/COPYING b/COPYING
index be4b2912..d9c012c1 100644
--- a/COPYING
+++ b/COPYING
@@ -13,8 +13,8 @@ Some of Shotwell's icons are copyright their respective authors:
       https://launchpad.net/breathe-icon-set
       Licensed under Creative Commons Attribution ShareAlike 3.0
       
-    * gnome-icon-theme
-      http://git.gnome.org/browse/gnome-icon-theme
+    * adwaita-icon-theme (previously called gnome-icon-theme)
+      https://gitlab.gnome.org/GNOME/adwaita-icon-theme/
       Licensed under Creative Commons Attribution ShareAlike 3.0