UI: Selectively disable focus frame

NoFocusFrameStyle was meant to disable focus frames around the scenes/sources
list (on OSX); unfortunately it also removed focus frames from controls that
should have focus frames like input boxes in the settings window

obs/window-basic-source-select.cpp

@@ -164,6 +164,8 @@ OBSBasicSourceSelect::OBSBasicSourceSelect(OBSBasic *parent, const char *id_)
 {
 	ui->setupUi(this);
 
+	ui->sourceList->setAttribute(Qt::WA_MacShowFocusRect, false);
+
 	QString placeHolderText{QT_UTF8(obs_source_get_display_name(
 				OBS_SOURCE_TYPE_INPUT, id))};