WiFi config - Mention clearing stored credentials

[patridge]

https://developer.wildernesslabs.co/Meadow/Meadow.OS/Configuration/WiFi_Configuration/ (GitHub)

After setting any SSID+password in config, it seems to be stored until explicitly cleared. According to the Networking page, you can deploying a wifi.config.yaml with the ClearDefaultCredentials: true field set. But this isn't mentioned on the WiFi config page.