Bump transformers in /doc/source/tutorials/voice_cloning

Bumps [transformers](https://github.com/huggingface/transformers) from 4.33.3 to 4.38.0.
- [Release notes](https://github.com/huggingface/transformers/releases)
- [Commits](huggingface/transformers@v4.33.3...v4.38.0)

---
updated-dependencies:
- dependency-name: transformers
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

doc/source/tutorials/voice_cloning/requirements.txt

@@ -8,5 +8,5 @@ soundfile==0.12.1
 streamlit==1.28.1
 torch==2.1.0
 torchaudio==2.1.0
-transformers==4.33.3
+transformers==4.38.0
 TTS==0.19.1