Mention that Spark 4 wifi is disabled when ethernet is connected.

[steersbob]

For technical reasons, the Spark 4 can't simultaneously operate its ethernet / Wi-Fi / bluetooth adapters. When both are available, ethernet connections take precedence, and the Wi-Fi adapter is disabled. This is somewhat intuitive, and the connected ethernet cable is a strong indicator that the user wishes to use the more reliable cabled connection. However, this behavior is not described clearly in documentation.