vnc: drop QERR_VNC_SERVER_FAILED

We now always return "nice" error messages in errp when we goto fail.
Drop the default error message.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/qerror.h b/qerror.h
index c91708c..f23b978 100644
--- a/qerror.h
+++ b/qerror.h
@@ -237,9 +237,6 @@
 #define QERR_VIRTFS_FEATURE_BLOCKS_MIGRATION \
     ERROR_CLASS_GENERIC_ERROR, "Migration is disabled when VirtFS export path '%s' is mounted in the guest using mount_tag '%s'"
 
-#define QERR_VNC_SERVER_FAILED \
-    ERROR_CLASS_GENERIC_ERROR, "Could not start VNC server on %s"
-
 #define QERR_SOCKET_CONNECT_FAILED \
     ERROR_CLASS_GENERIC_ERROR, "Failed to connect to socket"
 
diff --git a/ui/vnc.c b/ui/vnc.c
index 9377569..d0ffcc5 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -3088,9 +3088,6 @@
     return;
 
 fail:
-    if (!error_is_set(errp)) {
-        error_set(errp, QERR_VNC_SERVER_FAILED, display);
-    }
     g_free(vs->display);
     vs->display = NULL;
 }