[partition] Remove unused attribute m_defaultFsType

This attribute is used since the commit fcd0e8d36 [partition] Apply
partition layout when replacing free space

src/modules/partition/gui/ChoicePage.cpp

@@ -90,14 +90,8 @@ ChoicePage::ChoicePage( Config* config, QWidget* parent )
     auto gs = Calamares::JobQueue::instance()->globalStorage();
 
     m_requiredPartitionTableType = gs->value( "requiredPartitionTableType" ).toStringList();
-    m_defaultFsType = gs->value( "defaultFileSystemType" ).toString();
     m_enableEncryptionWidget = gs->value( "enableLuksAutomatedPartitioning" ).toBool();
 
-    if ( FileSystem::typeForName( m_defaultFsType ) == FileSystem::Unknown )
-    {
-        m_defaultFsType = "ext4";
-    }
-
     // Set up drives combo
     m_mainLayout->setDirection( QBoxLayout::TopToBottom );
     m_drivesLayout->setDirection( QBoxLayout::LeftToRight );

src/modules/partition/gui/ChoicePage.h

@@ -155,7 +155,6 @@ private:
     int m_lastSelectedActionIndex = -1;
 
     QStringList m_requiredPartitionTableType;
-    QString m_defaultFsType;
     bool m_enableEncryptionWidget;
 
     QMutex m_coreMutex;