[partition] Translate bootloader location combo box

If you switch languages, and then go to the partition
page, and pick "manual", the combo-box entries would
not be translated until **after** you do something
(e.g. edit a partition).

Now they are re-translated when the language changes.

src/modules/partition/gui/PartitionPage.cpp

@@ -115,7 +115,10 @@ PartitionPage::PartitionPage( PartitionCoreModule* core, QWidget* parent )
         m_ui->label_3->hide();
     }
 
-    CALAMARES_RETRANSLATE( m_ui->retranslateUi( this ); );
+    CALAMARES_RETRANSLATE(
+        m_ui->retranslateUi( this );
+        m_core->bootLoaderModel()->update(); // Need to re-translate entries in the combo-box
+    );
 }
 
 PartitionPage::~PartitionPage() {}