Udate url, as upstream finally learnt how to use TLS

Signed-off-by: David Runge <dvzrv@archlinux.org>

PKGBUILD

@@ -12,7 +12,7 @@ pkgver=3.8.2
 pkgrel=1
 pkgdesc="Fast, easy to administer, secure mail server"
 arch=(x86_64)
-url="http://www.postfix.org/"
+url="https://www.postfix.org/"
 license=(EPL)
 depends=(glibc)
 makedepends=(