chore(deps): bump sentencepiece in /generative_ai/extensions

Bumps [sentencepiece](https://github.com/google/sentencepiece) from 0.2.0 to 0.2.1.
- [Release notes](https://github.com/google/sentencepiece/releases)
- [Commits](google/sentencepiece@v0.2.0...v0.2.1)

---
updated-dependencies:
- dependency-name: sentencepiece
  dependency-version: 0.2.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

generative_ai/extensions/requirements.txt

@@ -4,7 +4,7 @@ pandas==2.2.3; python_version > '3.8'
 pillow==10.4.0; python_version < '3.8'
 pillow==10.4.0; python_version >= '3.8'
 google-cloud-aiplatform[all]==1.69.0
-sentencepiece==0.2.0
+sentencepiece==0.2.1
 google-auth==2.38.0
 anthropic[vertex]==0.28.0
 langchain-core==0.2.33