cmake-gui: Clarify help string on toolset selection field

The text `-T parameter` may be read as an example value for the field,
but the `-T` part should not be included.  Clarify the wording.

Closes: #16475

Source/QtDialog/FirstConfigure.cxx

@@ -56,7 +56,7 @@ QFrame* StartCompilerSetup::CreateToolsetWidgets()
   QVBoxLayout* l = new QVBoxLayout(frame);
   l->setContentsMargins(0, 0, 0, 0);
 
-  ToolsetLabel = new QLabel(tr("Optional toolset to use (-T parameter)"));
+  ToolsetLabel = new QLabel(tr("Optional toolset to use (argument to -T)"));
   l->addWidget(ToolsetLabel);
 
   Toolset = new QLineEdit(frame);