Bump splink from 3.9.4 to 4.0.1 in /python

Bumps [splink](https://github.com/moj-analytical-services/splink) from 3.9.4 to 4.0.1.
- [Release notes](https://github.com/moj-analytical-services/splink/releases)
- [Changelog](https://github.com/moj-analytical-services/splink/blob/master/CHANGELOG.md)
- [Commits](moj-analytical-services/splink@v3.9.4...v4.0.1)

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

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

python/setup.cfg

@@ -19,7 +19,7 @@ packages = find:
 python_requires = >=3.7.0
 install_requires =
     ipython==7.22.0
-    splink==3.9.4
+    splink==4.0.1
 
 [options.package_data]
 arc =