Bump bleach from 6.2.0 to 6.4.0 in /notebook_python

Bumps [bleach](https://github.com/mozilla/bleach) from 6.2.0 to 6.4.0.
- [Changelog](https://github.com/mozilla/bleach/blob/main/CHANGES)
- [Commits](mozilla/bleach@v6.2.0...v6.4.0)

---
updated-dependencies:
- dependency-name: bleach
  dependency-version: 6.4.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

notebook_python/requirements_notebook.txt

@@ -7,7 +7,7 @@ async-lru==2.0.5
 attrs==25.3.0
 babel==2.17.0
 beautifulsoup4==4.14.2
-bleach==6.2.0
+bleach==6.4.0
 certifi==2025.8.3
 cffi==2.0.0
 charset-normalizer==3.4.3