doc/wifi: small fixup
doc/wifi: small fixup

The WiFi station connect sequence diagram does not have any "successful" ending.
It looks like a copy-paste error, because there are two consequent `SYSTEM_EVENT_STA_DISCONNECTED` events firing with nothing happening in between.

I think the original meaning was that the last event should be `SYSTEM_EVENT_STA_CONNECTED` to signify that if all goes well, that is the event that will be fired.

Merges https://github.com/espressif/esp-idf/pull/2065

armada-ai/esp-idf,www220/esp-idf,espressif/esp-idf,espressif/esp-idf,armada-ai/esp-idf,mashaoze/esp-idf,espressif/esp-idf,www220/esp-idf,mashaoze/esp-idf,armada-ai/esp-idf,mashaoze/esp-idf,mashaoze/esp-idf,espressif/esp-idf,www220/esp-idf,mashaoze/esp-idf,www220/esp-idf,www220/esp-idf,armada-ai/esp-idf