UI: Fix certain buttons turning up white in dark theme

Fixes the browse button in the remux file dialog not having the proper
style applied. This is a bit of a workaround because it is still unknown
why the button was white.

UI/window-basic-main.cpp

@@ -53,6 +53,7 @@
 #include "window-remux.hpp"
 #include "qt-wrappers.hpp"
 #include "context-bar-controls.hpp"
+#include "obs-proxy-style.hpp"
 #include "display-helpers.hpp"
 #include "volume-control.hpp"
 #include "remote-text.hpp"
@@ -217,6 +218,7 @@ OBSBasic::OBSBasic(QWidget *parent)
 
 	ui->setupUi(this);
 	ui->previewDisabledWidget->setVisible(false);
+	ui->contextContainer->setStyle(new OBSProxyStyle);
 
 	startingDockLayout = saveState();