fix: flush audio in SarvamTTSService

[markbackman]

Please describe the changes in your PR. If it is addressing an issue, please reference that as well.

Found this in looking into an issue for another TTS provider.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/pipecat/services/sarvam/tts.py	0.00%	2 Missing :warning:

Files with missing lines	Coverage Δ
src/pipecat/services/sarvam/tts.py	0.00% <0.00%> (ø)

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