Don't mention cut buffers

We haven't supported them in a long time so we shouldn't mention
them in the interface and documentation.
diff --git a/vncviewer/parameters.cxx b/vncviewer/parameters.cxx
index 1151a7c..ad82f27 100644
--- a/vncviewer/parameters.cxx
+++ b/vncviewer/parameters.cxx
@@ -127,7 +127,7 @@
                             "Send clipboard changes to the server", true);
 #if !defined(WIN32) && !defined(__APPLE__)
 BoolParameter sendPrimary("SendPrimary",
-                          "Send the primary selection and cut buffer to the "
+                          "Send the primary selection to the "
                           "server as well as the clipboard selection",
                           true);
 #endif