UI: Set remove prompt default action

Resolves an issue on macOS where the default action is not set for
prompts when the user is removing one or multiple sources or scenes.

UI/window-basic-main.cpp

@@ -3233,8 +3233,9 @@ bool OBSBasic::QueryRemoveSource(obs_source_t *source)
 
 	QMessageBox remove_source(this);
 	remove_source.setText(text);
-	QAbstractButton *Yes =
+	QPushButton *Yes =
 		remove_source.addButton(QTStr("Yes"), QMessageBox::YesRole);
+	remove_source.setDefaultButton(Yes);
 	remove_source.addButton(QTStr("No"), QMessageBox::NoRole);
 	remove_source.setIcon(QMessageBox::Question);
 	remove_source.setWindowTitle(QTStr("ConfirmRemove.Title"));
@@ -4996,8 +4997,9 @@ void OBSBasic::on_actionRemoveSource_triggered()
 
 		QMessageBox remove_items(this);
 		remove_items.setText(text);
-		QAbstractButton *Yes = remove_items.addButton(
-			QTStr("Yes"), QMessageBox::YesRole);
+		QPushButton *Yes = remove_items.addButton(QTStr("Yes"),
+							  QMessageBox::YesRole);
+		remove_items.setDefaultButton(Yes);
 		remove_items.addButton(QTStr("No"), QMessageBox::NoRole);
 		remove_items.setIcon(QMessageBox::Question);
 		remove_items.setWindowTitle(QTStr("ConfirmRemove.Title"));