Update copyright-format URL to use HTTPS.

debian/changelog

+python-mapnik (1:0.0~20170621-0cd7493f2-3) UNRELEASED; urgency=medium
+
+  * Update copyright-format URL to use HTTPS.
+
+ -- Bas Couwenberg <sebastic@debian.org>  Sun, 21 Jan 2018 10:37:43 +0100
+
 python-mapnik (1:0.0~20170621-0cd7493f2-2) unstable; urgency=medium
 
   * Bump Standards-Version to 4.1.1, no changes.

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: python-mapnik
 Upstream-Contact: https://github.com/mapnik/python-mapnik/issues
 Source: https://github.com/mapnik/python-mapnik