Revert "Cocoa: make dialogs emit the "selected" signals"

This reverts commit dfa8854cf7 and
removes all "selected" signal emissions from the Cocoa platform
dialogs.

Even though it fixed the new QML dialogs that were relying on the
"selected" signals, it lead to duplicate signals with QColorDialog,
QFileDialog, and QFontDialog. We'll fix the new QML dialogs to not
rely on the selected signals, but handle it on accept the same way
than QtWidgets and QtQuick Dialogs do, so there is no need to repeat
the signals in all platform plugins.

Task-number: QTBUG-55299
Change-Id: I35e08cee92a4454544497b027ed10abad6c26673
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/plugins/platforms/cocoa/qcocoacolordialoghelper.mm

@@ -177,8 +177,6 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSColorPanelDelegate);
 {
     Q_UNUSED(notification);
     [self updateQtColor];
-    if (mHelper)
-        emit mHelper->colorSelected(mQtColor);
 }
 
 - (void)windowWillClose:(NSNotification *)notification

src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm

@@ -582,15 +582,6 @@ void QCocoaFileDialogHelper::QNSOpenSavePanelDelegate_panelClosed(bool accepted)
     QCocoaMenuBar::resetKnownMenuItemsToQt();
     if (accepted) {
         emit accept();
-
-        QString filter = selectedNameFilter();
-        if (filter.isEmpty())
-            emit filterSelected(filter);
-
-        QList<QUrl> files = selectedFiles();
-        emit filesSelected(files);
-        if (files.count() == 1)
-            emit fileSelected(files.first());
     } else {
         emit reject();
     }

src/plugins/platforms/cocoa/qcocoafontdialoghelper.mm

@@ -365,7 +365,6 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSFontPanelDelegate);
                 emit mHelper->reject();
             } else {
                 emit mHelper->accept();
-                emit mHelper->fontSelected(mHelper->currentFont());
             }
         }
     }