Bump transformers from 4.52.4 to 5.15.1

Bumps [transformers](https://github.com/huggingface/transformers) from 4.52.4 to 5.15.1.
- [Release notes](https://github.com/huggingface/transformers/releases)
- [Commits](https://github.com/huggingface/transformers/compare/v4.52.4...v5.15.1)

---
updated-dependencies:
- dependency-name: transformers
  dependency-version: 5.15.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -16,7 +16,7 @@ clean-text==0.6.0
 unidecode==1.4.0
 spacy==3.8.11
 torch==2.9.1
-transformers==4.52.4
+transformers==5.15.1
 ffmpeg-python==0.2.0
 elevenlabs==1.57.0
 yt-dlp==2025.10.22