sip: media-pipeline: Remove lport-rtp and lport-rtcp property

We're not setting the desired ports from the outside anymore, but rather
querying the ports that have been allocated by the operating system.

Therefore the lport-rtp and lport-rtcp property have become superfluous and are
being removed. We also adapt to changes outside of the pipeline code.

plugins/sip/calls-sip-util.h

@@ -62,4 +62,3 @@ gboolean              check_sips                         (const char *addr);
 gboolean              check_ipv6                         (const char *host);
 const char           *get_protocol_prefix                (const char *protocol);
 gboolean              protocol_is_valid                  (const char *protocol);
-guint                 get_port_for_rtp                   (void);