Better looking status bar under Linux Ubuntu (#2662)

* Remove borders from status bar items

On Ubuntu the status bar didn't look as good as on Windows due to some border being drawn around each status bar cell.

src/citra_qt/main.cpp

@@ -115,6 +115,7 @@ void GMainWindow::InitializeWidgets() {
         statusBar()->addPermanentWidget(label);
     }
     statusBar()->setVisible(true);
+    setStyleSheet("QStatusBar::item{border: none;}");
 }
 
 void GMainWindow::InitializeDebugWidgets() {