sip: media-manager: Don't include sofia-sip/nua.h in public header

It isn't needed in the implementation either. It was only useful because it
included system headers like sys/types.h and sys/socket.h which we should now
include directly.

This will make it easier to move the media manager into the core sources.

plugins/sip/calls-sip-media-manager.c

@@ -30,6 +30,11 @@
 
 #include <gst/gst.h>
 
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+
+
 /**
  * SECTION:sip-media-manager
  * @short_description: The media manager singleton

plugins/sip/calls-sip-media-manager.h

@@ -26,7 +26,6 @@
 
 #include "gst-rfc3551.h"
 
-#include <sofia-sip/nua.h>
 #include <sofia-sip/sdp.h>
 #include <glib-object.h>