[welcome] Switch model to a list model

- There doesn't seem to be a real benefit to providing the
   name and label as separate columns.

src/modules/welcome/LocaleModel.cpp

@@ -19,7 +19,7 @@
 #include "LocaleModel.h"
 
 LocaleModel::LocaleModel( const QStringList& locales, QObject* parent )
-    : QAbstractTableModel( parent )
+    : QAbstractListModel( parent )
 {
     Q_ASSERT( locales.count() > 0 );
     m_locales.reserve( locales.count() );
@@ -32,12 +32,6 @@ LocaleModel::~LocaleModel()
 {
 }
 
-int
-LocaleModel::columnCount( const QModelIndex& ) const
-{
-    return 2;
-}
-
 int
 LocaleModel::rowCount( const QModelIndex& ) const
 {

src/modules/welcome/LocaleModel.h

@@ -19,13 +19,13 @@
 #ifndef WELCOME_LOCALEMODEL_H
 #define WELCOME_LOCALEMODEL_H
 
-#include <QAbstractTableModel>
+#include <QAbstractListModel>
 #include <QVector>
 
 
 #include "utils/LocaleLabel.h"
 
-class LocaleModel : public QAbstractTableModel
+class LocaleModel : public QAbstractListModel
 {
 public:
     using LocaleLabel = CalamaresUtils::LocaleLabel;
@@ -34,7 +34,6 @@ public:
     virtual ~LocaleModel() override;
 
     int rowCount( const QModelIndex& parent ) const override;
-    int columnCount( const QModelIndex& parent ) const override;
 
     QVariant data( const QModelIndex& index, int role ) const override;