Bump version to 3.4.1

- Fix support of PyMongo 4
- Add configurable subject_identifier_uri to clients
- fix: example/requirements.txt to reduce vulnerabilities
- fix: userinfo: avoid indexing by None user_id in stateless mode

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

setup.py

@@ -2,7 +2,7 @@
 
 setup(
     name='pyop',
-    version='3.4.0',
+    version='3.4.1',
     packages=find_packages('src'),
     package_dir={'': 'src'},
     url='https://github.com/IdentityPython/pyop',