update git URLs (git -> https; gitea)

Change-Id: I56d19d28078c6e8a381dc155ca1001d39621ef1d
diff --git a/debian/copyright b/debian/copyright
index f6a5956..0615b84 100644
--- a/debian/copyright
+++ b/debian/copyright
@@ -1,6 +1,6 @@
 Format: http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
 Upstream-Name: osmo-gbproxy
-Source: git://git.osmocom.org/osmo-gbproxy
+Source: https://gitea.osmocom.org/cellular-infrastructure/osmo-gbproxy
 
 Files:     .gitignore
            .gitreview