COMP: Fix deprecated use of QFileDialog::DirectoryOnly in ctkFileDial…

…ogTest1

This commit fixes the following warning:

/path/to/CTK/Libs/Widgets/Testing/Cpp/ctkFileDialogTest1.cpp:47:40: warning: ‘QFileDialog::DirectoryOnly’ is deprecated: Use setOption(ShowDirsOnly, true) instead [-Wdeprecated-declarations]
   47 |   fileDialog->setFileMode(QFileDialog::DirectoryOnly);
      |                                        ^~~~~~~~~~~~~

Libs/Widgets/Testing/Cpp/ctkFileDialogTest1.cpp

@@ -44,7 +44,8 @@ int testSelectionMode(ctkFileDialog* fileDialog)
   CHECK_INT(fileDialog->selectionMode(), static_cast<int>(QAbstractItemView::SingleSelection));
 
   fileDialog->setSelectionMode(QAbstractItemView::ExtendedSelection);
-  fileDialog->setFileMode(QFileDialog::DirectoryOnly);
+  fileDialog->setFileMode(QFileDialog::Directory);
+  fileDialog->setOption(QFileDialog::ShowDirsOnly);
   CHECK_INT(fileDialog->selectionMode(), static_cast<int>(QAbstractItemView::SingleSelection));
 
   fileDialog->setSelectionMode(QAbstractItemView::ExtendedSelection);