pin of `z3c.dependencychecker==3.0` fails with Python3.10

`z3c.dependencychecker==3.0` is only available for Python 3.11 and higher

```
[testenv:dependencies]
description = check if the package defines all its dependencies
skip_install = true
deps =
    build
    z3c.dependencychecker==3.0
commands =
    python -m build --wheel
    dependencychecker
```