docs(samples): Update code samples for adaptation and VAD

[nitsanshai]

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[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/transcribe_streaming_voice_activity_events.py:18, tag speech_transcribe_streaming_voice_activity_events
• samples/snippets/transcribe_streaming_voice_activity_timeouts.py:18, tag speech_transcribe_streaming_voice_activity_timeouts

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