fix: wrong default port in docs (#40665)

fix: wrong default port

docs/tutorial/debugging-main-process.md

@@ -14,10 +14,10 @@ process:
 
 Electron will listen for V8 inspector protocol messages on the specified `port`,
 an external debugger will need to connect on this port. The default `port` is
-`5858`.
+`9229`.
 
 ```shell
-electron --inspect=5858 your/app
+electron --inspect=9229 your/app
 ```
 
 ### `--inspect-brk=[port]`