Add "ca-certificates" recommends to apt-transport-https

The rational is that https downloads fail with cryptic error messages
if the certificates are missing.

debian/control

@@ -121,6 +121,7 @@ Description: package management related utility programs
 Package: apt-transport-https
 Architecture: any
 Depends: ${shlibs:Depends}, ${misc:Depends}
+Recommends: ca-certificates
 Priority: optional
 Description: https download transport for APT
  This package enables the usage of 'deb https://foo distro main' lines