Fix some issues reported by lintian

See merge request debian-astro-team/casacore-data-igrf!1

Fixes: lintian: uses-debhelper-compat-file
See-also: https://lintian.debian.org/tags/uses-debhelper-compat-file.html

Fixes: lintian: package-uses-old-debhelper-compat-version
See-also: https://lintian.debian.org/tags/package-uses-old-debhelper-compat-version.html

Fixes: lintian: homepage-field-uses-insecure-uri
See-also: https://lintian.debian.org/tags/homepage-field-uses-insecure-uri.html

Fixes: lintian: insecure-copyright-format-uri
See-also: https://lintian.debian.org/tags/insecure-copyright-format-uri.html

with Debian dir 57d6215496e505a126a6e88cbe7f03df29221960