iOS: User needs to re-try connecting if micro:bit is forgotten

[microbit-grace]

Repro steps:

1. Successfully connect and flash a MakeCode program to the micro:bit on iOS.
2. Forget micro:bit.
3. Try to connect and flash MakeCode program again. Click “Pair” when asked.
4. See partial flashing get interrupted and see “Try again” dialog.

Workaround:
Trying again should work provided “Pair” was selected in step 3.

Possible options to address this issue:

1. Automatically re-try partial flashing once if it gets interrupted. This might look a bit weird to the user because the progress bar would restart from 0 again.
2. Tailor the "Try again” dialog for this scenario. Explain in the “Try again” dialog that trying again should work. Maybe only try the partial flashing part of the process when "Try again is clicked”.