build(deps): update snowballstemmer requirement from <3.0 to <4.0

Updates the requirements on [snowballstemmer](https://github.com/snowballstem/snowball) to permit the latest version.
- [Changelog](https://github.com/snowballstem/snowball/blob/master/NEWS)
- [Commits](snowballstem/snowball@v2.0.0...v3.0.1)

---
updated-dependencies:
- dependency-name: snowballstemmer
  dependency-version: 3.0.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements-docs.txt

@@ -3,4 +3,4 @@ shibuya
 sphinx<8.2
 sphinx-autodoc-typehints[type_comments]>=1.8.0
 typing-extensions
-snowballstemmer<3.0
+snowballstemmer<4.0