Enable test_docker_pre after pinning the mpmath transitive dependency (#6481)

Finalizes #6475

Author: pavoljuhas

dev_tools/docker_test.py

@@ -22,7 +22,6 @@ def test_docker_stable():
     assert result.returncode == 0
 
 
-@pytest.mark.skip(reason="fails due to boken dependendencies #6475")
 def test_docker_pre():
     if platform.system() != 'Linux':
         pytest.skip("Unsupported os")