debian: Update copyright format link to use HTTPS

Resolves: lintian: insecure-copyright-format-uri
Signed-off-by: Valters Jansons <valter.jansons@gmail.com>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

debian/copyright

-Format: http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
 Upstream-Name: libloc
 Upstream-Contact: Michael Tremer <michael.tremer@ipfire.org>
 Source: https://location.ipfire.org/download