Remove a call to metadata_box.resize_columns

It has been removed in af184bc.

Fixes PICARD-775.

picard/ui/mainwindow.py

@@ -895,7 +895,6 @@ class MainWindow(QtGui.QMainWindow):
         """Show/hide the cover art box."""
         if self.show_cover_art_action.isChecked():
             self.cover_art_box.show()
-            self.metadata_box.resize_columns()
         else:
             self.cover_art_box.hide()