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/OptionsDialog.cxx b/vncviewer/OptionsDialog.cxx
index 55a366f..2f9df9c 100644
--- a/vncviewer/OptionsDialog.cxx
+++ b/vncviewer/OptionsDialog.cxx
@@ -720,7 +720,7 @@
   sendPrimaryCheckbox = new Fl_Check_Button(LBLRIGHT(tx, ty,
                                                      CHECK_MIN_WIDTH,
                                                      CHECK_HEIGHT,
-                                                     _("Send primary selection and cut buffer as clipboard")));
+                                                     _("Send primary selection as clipboard")));
   ty += CHECK_HEIGHT + TIGHT_MARGIN;
 #endif