[Listen] Old speech copy in output label when Speech services unavailable

[rowildcard]

Describe the bug

If Listen has been in use when Siri & Dictation are disabled, the output label should not persist any questions or answers from when it was last used.

To Reproduce

Pre-requisites

Speech and microphone access have been granted for Listen. At least one or both of the Siri and Keyboard dictation system options are enabled.

Steps

1. On the Listen category, speak a question.

   As expected, the question appears in the output label.

2. Go to system settings and disable Siri & Dictation in Screen Time.
3. Foreground the app. The Listen category is displayed.

   The speech services unavailable message appears.

Expected behavior The output label is blank

Actual behavior The output label shows the last question/answer

Screenshots

Device Information

iOS 15.0.2 iPhone 12 Max Pro TestFlight build 2835

[rowildcard]

Test verified. iPhone 12 Max Pro, iOS 15.0.2