Remove unnecessary build warning

KDialog::makeStandardCaption() is not necessary anymore.

Quoting David:
    I made Qt add the application name to the titlebar automatically on
    desktop platforms. So don't add it again in the application code.

From https://mail.kde.org/pipermail/kde-frameworks-devel/2014-August/018143.html

ui/presentationwidget.cpp

@@ -150,7 +150,6 @@ PresentationWidget::PresentationWidget( QWidget * parent, Okular::Document * doc
         caption = doc->currentDocument().fileName();
     caption = i18nc( "[document title/filename] – Presentation", "%1 – Presentation", caption );
     setWindowTitle( caption );
-#pragma message("KF5: Here was a makeStandardCaption, lost in KF5 port")
 
     m_width = -1;
     m_screen = -2;