c74fb68 breaks service advertisement on PicoW

[kortschak]

While investigating #315 I noticed that I was unable to get my demonstrator to work with the tip of dev. I re-confirmed that the change I submitted in #314 does work on release, and release with the soypat/cyw43439 go.mod dep requirement only specified in the consuming module also works.

Repro:

1. In one terminal

   $ tinygo flash -target pico-w -stack-size=8kb -monitor -x ./receiver
   

2. In another

   $ go run ./sender
   

3. Confirm that the Pico W emits the expected text (this requires that the local code run at least twice), and the local code behaves as expected (does not require a second run).

Now $ go get tinygo.org/x/bluetooth@dev and retry. The local code will find the device and then timeout searching for the service.

Bisected to c74fb68. See comment in go.mod file.