Fix second-instance handler signature (#14731)

docs/api/app.md

@@ -806,7 +806,7 @@ const gotTheLock = app.requestSingleInstanceLock()
 if (!gotTheLock) {
   app.quit()
 } else {
-  app.on('second-instance', (commandLine, workingDirectory) => {
+  app.on('second-instance', (event, commandLine, workingDirectory) => {
     // Someone tried to run a second instance, we should focus our window.
     if (myWindow) {
       if (myWindow.isMinimized()) myWindow.restore()